Table of Contents Executive Summary ………………………………………………………………...ii 1.0 Introduction ………………………………………….………………… 1 2.0 General Description of the Heron Pond Natural Area ...………………. 1 3.0 Existing Environment ………………………………….……………… 2 4.0 Conservation Values of the Heron Pond Natural Area .……………….. 7 5.0 Local Land Use ………………………………………………………… 8 6.0 Threats to the Heron Pond Natural Area ………………………………. 9 7.0 Vision for the Heron Pond Natural Area ………………………………. 9 8.0 Goals for the Heron Pond Natural Area ………………………………… 9 9.0 Objectives for the Heron Natural Area ………………………………… 10 10.0 Management Policies for the Heron Pond Natural Area ……………….. 11 11.0 Action Steps …………………………………………………………….. 13 12.0 References ……………………………………………………………… 14 List of Tables Table 1. Plant Species Observed at Heron Pond ……………………………… 16 Table 2. Breeding Bird Species Associated with Habitats Found at Heron Pond 18 Table 3. Summary of sizes, ownership, and organizational responsibilities for

the three parcels that comprise the Heron Pond Natural Area ……….. 19 List of Figures Figure 1. Location of the Heron Pond Natural Area.…………………………… 20 Figure 2. Boundaries of the Heron Pond Natural Area.………………………… 21 Figure 3. Surficial Geology of the Heron Pond Natural Area …………………… 22 Figure 4. Locations of Toxic Materials and the Proposed Stormwater

Detention Pond at the Heron Pond Expansion (Heller) Property ……… 23 Appendices Appendix 1. Contacts List Appendix 2. Aerial Photo of Site Appendix 3. Breeding Bird Atlas Data for Commerce City USGS Quadrangle Map Appendix 4. Weed Management Plan Appendix 5. Native Plant Community Restoration Plan Appendix 6. Natural Areas Program of the City of Denver Parks Department

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Executive Summary

The City and County of Denver (Denver) is pursuing a major urban park and open

space project along the South Platte River. The 46-acre Heron Pond Natural Area will be created by combining three parcels. One is the existing 18-acre Heron Pond parcel that is owned by Denver and managed by the City’s Wastewater Management Division as a stormwater detention pond. Another parcel is the 25-acre Heron Pond expansion (a portion of the Heller property) which is located adjacent to Heron Pond in Adams County. With the help of the Great Outdoors Colorado (GOCO) Trust Fund, the State of Colorado Natural Resource Trustees, Adams County, the Urban Drainage and Flood Control District (UDFCD), and The Conservation Fund, Denver acquired the Heron Pond expansion property in December 1999. The property will be restored with native plant communities and modified to detain additional storm water. The Heron Pond Natural Area is adjacent to Northside Park which is scheduled for completion in the spring of 2000. Northside Park will link the Natural Area to a bike path and to the South Platte River Corridor network of trails, parks, and natural areas. The third parcel is a 2-3 acre strip of wetlands currently being constructed along the western side of Northside Park. Denver, along with Adams County and UDFCD, will be responsible for designing and constructing the new stormwater detention facilities on the Heron Pond expansion portion of the Natural Area. Denver will have primary responsibility for restoring and maintaining the Natural Area. This Management Plan is intended to serve as a guide for management of the Heron Pond Natural Area consisting of the 1) Heron Pond parcel, 2) the Heron Pond expansion parcel, and 3) the 2-3 acres of constructed wetlands. These parcels are shown in Figure 2.

Heron Pond will be an urban natural area. There will be limited opportunities for educational, scientific and passive recreational uses, which will be managed such that they will not significantly impair the natural values of the property. This plan covers the operation of the Natural Area from 1999 through 2004. The heart of the plan is a vision and sets goals, objectives, actions steps, and management policies for the Natural Area.

The vision for the Natural Area is as follows: Heron Pond Natural Area will be an

example of the historic South Platte River floodplain ecosystem and will serve as a sanctuary for wildlife and a place where people can experience and learn about nature. The Natural Area will also be a model for combining stormwater detention and restoration of wetland, riparian, and upland plant communities in an urban setting.

The goals for the Heron Pond Natural Area are to: 1) create and enhance natural

wildlife habitat; 2) detain stormwater runoff from the regional drainage basin, and use the stormwater to establish and sustain aquatic, wetland and riparian ecosystems; 3) create and maintain an urban open space area; and 4) create and maintain passive recreation opportunities for school groups and for the general public.

The following policies will guide the management of the Heron Pond Natural

Area and will help achieve its vision and goals.

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1) Human use of the Heron Pond Natural Area will be concentrated in the

wildlife viewing area in the southeast corner of the Natural Area to minimize adverse impacts of dispersed human use.

2) Active recreational activities such as ball games, soccer, and frisbee will not be allowed. Facilities for these activities will exist at the adjacent Northside Park.

3) Fishing, swimming and boating on Heron Pond are prohibited due to public safety considerations and to minimize impacts on wildlife. Boat access will be allowed as needed to monitor contaminants in Heron Pond.

4) Once restoration of the native plant communities is completed, removal or disturbance of native plants, animals or natural features is prohibited. This prohibition includes activities such as hunting, trapping, plant collecting, firewood collecting, cutting trees, and rock collecting. Exceptions may be made on a case-by-case basis as approved in advance in writing by the Manager, Denver Department of Parks and Recreation. This policy is not meant to prohibit prescribed burning, use of herbicides, mowing, cutting or grazing activities that are conducted to maintain native plant communities.

5) Motor vehicles will not be allowed except as required to support land management, stormwater detention pond construction and maintenance, or emergency response activities.

6) The following activities are also prohibited: subdivision of land; accumulating or dumping of trash; and commercial or industrial uses including but not limited to signs, timber harvesting, and mining.

7) Pets are not permitted except at the wildlife viewing facility and on the access path that connects the viewing facility to the parking area at Northside Park. All pets must be leashed and under the direct control of a responsible person at all times.

8) Heron Pond shall continue to function as an urban stormwater detention facility owned and operated by Denver Public Works. The Wastewater Management Division of the Denver Public Works Department, in conjunction with Adams County Public Works and assisted by the Urban Drainage, may periodically maintain the stormwater detention ponds and conveyance channels to remove accumulated sediment. It is acknowledged that maintenance of the stormwater detention facility will entail the use of heavy equipment to dredge and clean the ponds and that this will cause temporary adverse environmental impacts to the ponds, conveyance channels and equipment access routes. These impacts, including loud noises, the removal of vegetation, and loss of wildlife habitat, are expected to be temporary and will be minimized by Denver Public Works using best management practices.

9) Agencies and organizations involved in the management of the Heron Pond Natural Area shall notify and coordinate with other involved agencies and organizations and shall schedule and perform their activities so as to minimize adverse environmental impacts on the Natural Area to the extent practical. Involved agencies shall include at a minimum the Denver Department of

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Parks and Recreation, Denver Wastewater Management Division, Urban Drainage, Adams County Public Works Department, Colorado Department of Public Health and Environment, Colorado Division of Wildlife, and Colorado Open Lands.

10) All construction and maintenance of the stormwater detention facility (ponds, conveyance channels and access routes) at the Heron Pond Natural Area will be performed using best management practices recommended in the Urban Drainage and Flood Control District’s latest edition of the Urban storm Drainage Criteria Manual, Volume 3. Areas disturbed by construction and maintenance shall be restored promptly once construction or maintenance activities are completed in accordance with the Native Plant Community Restoration Plan that is appended to this Management Plan.

The Heron Pond Natural Area is being expanded and restored with the help of

several different organizations and government agencies. Significant funding to purchase the Heron Pond expansion property and to restore the property to natural and semi-natural conditions has been provided through contributions from GOCO, the State of Colorado Natural Resource Trustees, Adams County, and Urban Drainage.

Colorado Open Lands (COL), a Colorado non-profit organization, will be the

recipient of a conservation easement over the Heron Pond and the constructed wetland portions of the Natural Area and will monitor the property to ensure that the Management Plan for the Natural Area is being implemented. In addition, Denver has purchased the Heron Pond expansion property and accepted a Declaration of Covenants, Conditions and Restrictions that places certain requirements on the property related to open space, wildlife habitat, and restoration. This Declaration places GOCO and COL in enforcement and monitoring roles, respectively, regarding open space, wildlife habitat, and restoration of the Heron Pond expansion tract. The conservation easement will be donated to and the Declaration will be monitored by COL in order to restore and protect in perpetuity the significant relatively natural features and values of the property. All property that is acquired with GOCO and Colorado Natural Resource Damage funds shall be held and managed in perpetuity in a manner designed to protect its open space values, to prevent any development that would adversely affect such values, and where necessary and appropriate, to allow public access. The conservation easement and this Management Plan will serve those purposes.

A major component of the Heron Pond project will be the restoration of native plant communities in conjunction with the construction and operation of the stormwater detention pond. Appendices to plan outline scenarios for restoration and for management of noxious weeds.

Introduction

The purpose of this plan is to establish a vision and general management direction for the Heron Pond Natural Area for the period 1999–2004. This plan also includes specific recommendations for restoring native plant communities and controlling noxious weeds. The plan is the product of a joint effort between representatives of City and County of Denver (Denver), the members of the Wildlife and Natural Areas Task Force of the Mayor’s South Platte River Commission, representatives of the Urban Drainage and Flood Control District (Urban Drainage), Colorado Open Lands, Denver Department of Parks and Recreation, Colorado Department of Public Health and Environment, Colorado Division of Wildlife, Adams County Public Works Department, and the consultant. Representatives of the State Board of the Great Outdoors Colorado Trust Fund, Colorado Open Lands, and the Natural Resource Damage Trustees of the State of Colorado will provide input into this draft Management Plan, in accordance with the Declaration of Covenants, Conditions and Restrictions (Declaration) burdening the Heron Pond expansion parcel and the Conservation Easement burdening the Heron Pond and constructed wetlands parcels more fully described below. The Management Plan is consistent with the “Proposal – Natural Resource Damage Funds, Adams County/City and County of Denver, July 1998”, as required by the Declaration and the Conservation Easement.

General Description of the Heron Pond Natural Area Location and Size

The property is located in the City and County of Denver and Adams County, Colorado (Figure 1). The property is found on the Commerce City USGS 7½ minute quadrangle map, in the northwest ¼ of section 14, township 3 south, range 68 west of the 6th principal meridian. The entire Heron Pond Natural Area (the existing 18-acre Heron Pond parcel plus the 25-acre Heron Pond expansion portion of the property plus 2-3 acres of constructed wetland) will consist of approximately 46 acres of deeded ground. Legal descriptions of the three parcels that comprise the Heron Pond Natural Area are found in the Easement Documentation Report for the Heron Pond Natural Area. Access

From Interstate I-25, exit at 58th Avenue and turn east. Drive east on 58th Avenue for 0.4 mile until 58th Avenue meets Washington Street. Turn south (right) on Washington Street, and continue south along Washington until it intersects with 54th Avenue. Turn east (left) on 54th Avenue and drive for about ½ mile until 54th Avenue dead ends at Franklin Street. Turn south (right) on Franklin Street and drive south for about 1/3 mile to the National Guard Armory. Turn right (west) on 53rd Avenue and drive about 200 yards west to a parking area that serves Northside Park. From the parking area, walk north for about 50 yards to the Natural Area

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Alternatively, one can access the Natural Area from the south by continuing south of Washington Street. Turn east on 51st, and continue along 51st past Emerson Street until the road stops. This circle is the southern boundary of Northside Park (now under construction). Currently, one has to park here and walk about ¼ mile north through the site of Northside Park to reach the Natural Area. In the future, a somewhat different access from the south will be developed.

Boundaries

The northern boundary of the property is delineated by 54th Avenue (Figure 2). The western boundary is delineated by Washington Street except 1) in the northwest corner where the property abuts the Corvette Connection (5380 Washington St.), a shop that specializes in customizing Corvette automobiles, and 2) for a 2-acre tract along Washington Street south of Corvette Connection. The southern boundary is delineated by a chain link fence which abuts an vacant industrial site owned by Denver and the 13.4 acre Northside Park which is currently under construction. The eastern boundary abuts three businesses: USA Waste of Colorado, a solid waste recycling plant; Banner Rebar, a steel fabrication plant; and O.J. Watson Equipment, a truck conversion and customization shop. Addresses and telephone numbers of the neighboring landowners are found in the Contacts List in Appendix 1.

Existing Environment of the Heron Pond Natural Area Climate

The City of Denver receives a mean annual precipitation of 15.4 inches a year (Anonymous 1998c). The wettest months are May, June and July. The average daily high during the summer is 83.6 degrees F with July being the hottest month. The average daily high in the winter is 45.7 degrees F with January being the coldest month. On average, the temperature fails to rise above freezing only 23 days out of the year (Anonymous 1998c). Surficial Geology

The Heron Pond Natural Area is located in the floodplain of the South Platte River. The Geological Map of the Commerce City Quadrangle (Lindvall 1980) lists three types of alluvial material on the property.

Post-Piney Creek Alluvium: The dominant type of bedrock is Post-Piney Creek Alluvium deposits (designated as Qpp on Figure 3). It is characterized as light to dark-grayish-brown clay, silt, sand, and small amounts of gravel with dark-brown and dark-bluish-black humic bog clays (Lindvall 1980). Deposits that form the floodplains of major rivers and streams (like the South Platte) have high proportions of silt and sand with a thickness of as much as 5 feet (Lindvall 1980).

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Louviers Alluvium: The second type of bedrock is the Louviers Alluvium (designated as Qlo on Figure 3). It is characterized as a reddish to yellowish-brown pebbly arkosic sand, coarse sand, cobble gravel, with a few boulders (Lindvall 1980). This bedrock includes lenticular masses of silt and clay, commonly having contorted bedding. The coarse granular materials are stained and cemented locally by manganese and iron oxides, contain abundant mica, and are generally crossbedded (Lindvall 1980). Many exposures are found in pits excavated through younger alluvium deposits (as will likely occur during construction of the stormwater detention pond) (Lindvall 1980). This alluvium is commonly between 15-20 feet thick along the South Platte River. On the property, this type of bedrock is found exclusively around Heron Pond and was exposed during its construction.

Broadway Alluvium: The third type of bedrock is the Broadway Alluvium (designated as Qb on Figure 3). It is characterized as a pink to light-brown, generally well-stratified sand and gravel in well-defined terraces on the east side of the South Platte River valley (Lindvall 1980). The upper 2-3 feet are commonly a clayey to pebbly silt with an overall thickness of as much as 15 feet (Lindvall 1980). This type of alluvium is found exclusively in the northwest corner of the Natural Area.

Hydrology

The central feature of the Heron Pond Natural Area is the 15.25-acre Heron Pond. Heron Pond was built between 1977-78 as a storm water detention pond for the Globeville drainage basin. Until the fall of 1999, stormwater entered the pond through an open concrete channel (see aerial photograph in Appendix 2). About 300 feet of concrete channel immediately up-gradient from Heron Pond has been removed. As storm water enters the pond during a rainfall or snowmelt event, the level of water in the pond may rise temporarily while the stormwater is discharged through a pipe into the South Platte River. At other times, water is lost from the pond via leakage into the ground and to the atmosphere via evaporation. Stormwater runoff is the primary source of water on the property, the others being ground water discharge and direct precipitation. Environmental Hazards

The principal environmental hazard on the property is contaminated soil (also see Section 3.7). The contaminated soil resulted from local deposition of airborne materials discharged from the Globe smelter, mainly from the smokestack. Contaminants include cadmium, arsenic and mercury (Anonymous 1998a). The initial cleanup has been completed with the removal of most of the contaminated soil. The rest of the property was capped with an additional twelve inches of soil. Additional toxic material may be removed from the Heron Pond expansion parcel in order to accommodate future stormwater detention facilities.

The second environmental hazard on the property is Heron Pond itself. The pond

(particularly sediment on the bottom of the pond) is contaminated with various heavy metals from local industrial pollution (Anonymous 1998a). Although the contaminated

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sediment in the pond poses no immediate threat to humans, boating or tubing on, swimming in, and fishing in the pond are be prohibited.

The third environmental hazard on the property is flooding. The property lies within the flood plain of the South Platte River. Portions of the Natural Area lie within the 100-year flood plain (Anonymous 1995). Thus, there is a hazard from flooding mostly to visitor structures that will be constructed in the southeastern corner of the natural Area. The threat to human life from flooding appears very remote. Vegetation

Currently there is a narrow riparian area dominated by trees along the edge of Heron Pond. The dominant trees are plains cottonwood (Populus deltoides ssp. monilifera), peach-leaf willow (Salix amygdaloides), and Siberian elm (Ulmus pumila). Coyote willow (Salix exigua), which is a shrub, also occurs in patches around the pond margin (Table 1). A few Russian olive shrubs (Elaeagnus angustifolia) are also present. All of these are common, desirable, native species that are indigenous to wetland and riparian habitats along the South Platte, with the exception of Siberian elm and Russian olive, which are invasive, alien species. Cattail (Typha angustifolia) is present in the pond itself, mostly in the shallow areas at the inlet and in the northwest corner of the pond. The native upland shrub, rubber rabbitbrush (Chrysothamnus nauseosus ssp. graveolens) is present in small numbers.

Ground-layer vegetation on the uplands surrounding the pond consists mostly of alien weeds (Table 1). These include summer cypress (Kochia scoparia), Russian thistle (Salsola australis), field bindweed (Convovulus arvensis), diffuse knapweed (Acosta diffusa), cheatgrass (Anisantha tectorum), musk thistle (Carduus nutans), Canada thistle (Cirsium arvense), scotch thistle (Onopordum acanthium), puncturevine (Tribulus terrestris), alyssum (Alyssum minus), Jim Hill mustard (Sisymbrium altissimum), and Dalmatian toadflax (Linaria genistifolia ssp. dalmatica). Additional species of alien weeds undoubtedly exist in small patches that were overlooked or were not visible during field visits. The weed management plan in Appendix 4 identifies the highest-priority weed species for control and suggests ways to manage them.

Desirable, native ground layer plant species that are present on the uplands surrounding the pond include sand dropseed (Sporobolus cryptandrus), western wheatgrass (Pascopyrum smithii = Agropyron smithii), needle-and-thread (Stipa comata), purple three-awn (Aristida purpurea), side-oats grama (Bouteloua curtipendula) and aster (Machaeranthera sp.). Additionally, there are five mature cottonwood trees on the Heron Pond expansion parcel. These trees are supported by storm water that collects around the trees. An effort should be made to preserve these cottonwoods and promote the establishment of new cottonwoods on this part of the property.

The Colorado Natural Heritage Program searched its database for threatened and

endangered plant species and natural communities. The search identified one plant species that may occur in the general area. It is the showy prairie gentian (Eustoma

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grandiflora), a species that is ranked “globally secure” (G5) but “state rare” (S3). This species is found along streams, in wet meadows, pastures, and fields, usually near old stream meanders or at the margins of lakes or ponds on the plains. This species might be appropriate to establish at the Natural Area as part of the plant community restoration plan (see Appendix 5). Wildlife

Due to the close proximity of the South Platte River, the property is part of a wildlife corridor along the river. Some of the wildlife species that are known to use the South Platte River corridor and surrounding habitat area include mule deer (Odocoileus hemionus), coyote (Canus latrans), red fox (Vulpes vulpes), raccoon (Procylon lotor), skunk (Mephitis mephitis), porcupine (Eriethizon dorsatum), beaver (Cartor canadensis), muskrat (Ondatra zibethicus), Nuttall’s cottontail (Sylvilagus nuttallii), and black-tailed prairie dog (Cynomys ludovicianus) (Vicki Vargas-Madrid, pers. comm.). Red foxes have been observed repeatedly at Heron Pond during 1998-1999 (Marc Alston, pers. comm.). Mule deer (Odocoileus hemonius) is the only principal big game species in the area.

The Colorado Museum of Natural History sponsors the Breeding Bird Atlas program (Kingery 1998). Under the auspices of this program, volunteers have surveyed birds in a priority block in the southeastern corner of each US Geological Survey 7½ minute quadrangle map in Colorado. A priority block is a rectangle which is 3 miles (north-south) by 3½ miles (east-west) or one-sixth of a quadrangle. The Natural Area does not fall within a priority block. However, data are available for the Commerce City quadrangle in which the property is located. The Breeding Bird Atlas data indicate the bird species that one might expect to inhabit the property. In the Commerce City Quadrangle priority block, 52 bird species were recorded as observed (20), possible (7), probable (4), and confirmed (21) in 1995 (Breckon and Lentz 1995). This list of bird species for the Commerce City quadrangle is found in Appendix 3.

One of the main conservation values of the Heron Pond Natural Area is habitat for

waterfowl. The Breeding Bird Atlas includes the “Open Water Lakes”, “Open Water Streams”, “Emergent Wetlands Marshes”, and “Lowland Riparian” habitats in its surveys (Kingery 1998). Bird species that are associated with these habitats in Colorado are listed in Table 2.

During our visits on May 13, 1998, October 13, 1998, May 13, 1999, and October

20, 1999, we observed twenty-three species of birds. These species include: double-crested cormorant, Canada goose, mallard, pintail, white pelican, black-crowned night heron, great-blue heron, kingfisher, kestrel, black-billed magpie, American avocet, mourning dove, American robin, northern (red-shafted) flicker, barn swallow, red-winged blackbird, Brewer’s blackbird, Bullock’s oriole, brown-headed cowbird, starling, yellow warbler, chipping sparrow, and song sparrow.

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Heron Pond contains a population of carp, an alien fish (Cyprinus carpio). Flesh samples collected from carp from Heron Pond have been tested and determined to contain arsenic and mercury (Kirsten King, pers. comm.). Therefore, fishing will be prohibited at Heron Pond. Toxic Materials

The old Globe smelter operated by ASARCO, Inc. is located a few hundred yards west of Heron Pond immediately west of the intersection of 54th and Washington Streets (Figure 2). The plant currently produces lithage (lead oxide), bismuth oxide, test lead, and refines high-purity metals (Anonymous 1998a). The Globe Plant has been a processing site for various heavy metals since the 1880’s (Anonymous 1998a). The smelting operations left elevated levels of cadmium, lead, zinc, and arsenic in ground water, surface water, sediments and soil at and near the plant (Anonymous 1998b). An area around the Globe smelter, including all of the Heron Pond Natural Area, lies within the Superfund site. The State of Colorado Department of Public Health and Environment (CDPHE) has been the lead agency at this site.

Over many years, airborne and waterborne contaminants from the Globe smelter

site and other sources have contaminated Heron Pond with heavy metals. Sediment samples from the pond contained detectable levels of arsenic, nickel, cadmium, chromium, lead, mercury, silver, and copper (Kirsten King, pers. comm.). Water samples from the pond contained detectable levels of arsenic, cadmium, lead, and borderline detectable levels of mercury (Kirsten King, pers. comm.). However, these contaminants are not thought to pose a threat to humans as long as the sediment remains on the bottom of the pond and as long as people do not recreate in or on the pond or eat fish from the pond. Representatives of ASARCO will have access to the pond to collect water and sediment samples to monitor contaminants.

The Heron Pond expansion property (the upland area immediately west of Heron Pond) consists of approximately 25 acres of deeded ground. This property has been highly disturbed, and is dominated by alien weed species. In 1992, a hazardous materials assessment was conducted on the Heron Pond expansion parcel and found that the soil was contaminated with asbestos, arsenic, cadmium, lead, and zinc. The State of Colorado and ASARCO reached a settlement in 1993 to clean up the site (Anonymous 1998b). In 1996, ASARCO remediated the site by removing the most contaminated soil. The rest of the property was capped with twelve inches of soil. The cleanup was approved by CDPHE.

Additional follow-up environmental sampling of the Heron Pond expansion property was conducted in the fall and winter of 1998 and in the spring of 1999 to better understand the environmental contaminants on the property. URS Operating Services, Inc. conducted the sampling, under contract with the US Environmental Protection Agency. This sampling was conducted because the proposed use of the Heron Pond expansion property as a stormwater detention area could expose buried toxic materials to the atmosphere or could result in stormwater leaching through the toxic materials, with

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possible movement of toxic substances in ground water. The environmental sampling discovered no buried drums or metal tanks, plus there was no evidence of ground water contamination (Anonymous 1999). However, the sampling revealed the existence of buried animal rendering wastes, petroleum-contaminated soils, and metal-contaminated soils. The locations of these materials on the Heron Pond expansion property are shown in Figure 4.

Discovery of the metal-contaminated soil motivated a second round of sampling

to determine if the contaminated soils could be left on-site and to better estimate disposal costs. The report concluded that the metal-contaminated soil might meet the definition of “hazardous material” and is therefore not be disturbed under any circumstances. Environmental Services of the City and County of Denver recommended excavating the petroleum-contaminated soil and disposing of it at a solid waste landfill. Other material excavated to create the stormwater detention pond can be managed on-site, provided they are covered with one foot of clean soil, subject to CDPHE approval (Anonymous 1999). Denver Environmental Services suggested a modified perimeter for the stormwater detention pond, as shown in Figure 4 that would avoid the metal-contaminated soil and the animal rendering waste.

Conservation Values and Benefits of Heron Pond Natural Area

The conservation values of the Heron Pond Natural Area are natural, scenic, open space, wildlife habitat, and passive recreational values. The Heron Pond Natural Area will provide a number of benefits to the citizens of Denver and Adams County. These include: 1) habitat and buffer land for aquatic, wetland, and riparian wildlife species such as invertebrates, amphibians, songbirds, waterfowl, and small mammals; 2) native wetland, riparian and upland plant communities and species, including potentially the prairie gentian (Eustoma grandiflora) which is rare in Colorado; 3) limited opportunities for recreation such as a wildlife viewing area that would complement the active recreational amenity that will be provided by the future Northside Park which abuts the south side of the Natural Area; and 4) limited opportunities for passive recreational and educational uses. Denver will seek officially to designate the Heron Pond Natural Area as a Denver park. In addition, Denver has established a Natural Areas Program within the Department of Parks and Outdoor Recreation. Heron Pond Natural Area will be officially included in that program. Natural areas are classified in one of four ways: active use, conservation and restoration, preservation, and temporary preservation. Active use natural areas allow limited active recreation such as hard surface trails, fishing piers and other facilities that will attract public use. Conservation and restoration areas have significant natural features or the potential to restore them; activities will be geared toward the appreciation of the area’s natural features. Preservation areas are somewhat pristine in character and require protection. Human use of preservation areas will be discouraged. Temporary preservation areas are those closed for restoration. When restoration is completed, some activity will be allowed. Heron Pond is most appropriate as a “conservation and restoration” area.

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Local Land Use

The Heron Pond Natural Area is located west of the South Platte River in the

Globeville neighborhood at the northern edge of Denver (Figure 1). Heron Pond is located in an urban setting that is characterized by various industrial and commercial uses (Figure 2). Adjacent properties include the former City of Denver municipal sewage treatment facility, USA Waste of Colorado, Banner Rebar, OJ Watson Equipment, Iron and Metals Inc., the National Guard Armory, an unoccupied light industrial building, vacant land, and the ASARCO Globe Smelter.

The southeast boundary of the Heron Pond Natural Area abuts the 13.4 acre Northside Park, which is currently under development (Figure 2). The park lies atop Denver’s now demolished municipal wastewater treatment facility. This park will contain a soccer field, playground equipment, a picnic area, and a 2-3 acre created wetland that will be part of the Heron Pond Natural Area. Construction of the park began in March 1998 and is expected to be completed in November 1999. The Heron Pond Natural Area along with the adjacent Northside Park are important parts of the South Platte River Corridor project and will be linked by an adjacent trail to the main regional “Greenway” trail along the South Platte River.

The Natural Area has been created by combining three parcels. One is the existing Heron Pond parcel which is owned by Denver and managed by the City’s Wastewater Division. Another parcel is the Heron Pond expansion, a 25-acre portion of the Heller property in Adams County. With the help of the Great Outdoors Colorado Trust Fund, The Conservation Fund, and others, Denver acquired the Heron Pond expansion property in December 1999. The Heron Pond expansion property is currently vacant land and will be modified to detain additional storm water and will be restored with native plant riparian and upland plant communities west of Heron Pond. The third parcel is 2-3 acres of created wetlands along the western edge of Northside Park. The constructed wetlands parcel will serve as a channel and inlet for stormwater routed to the stormwater detention facility at the Natural Area.

As part of the settlement related to the Globe Superfund site, the State of

Colorado received payment from ASARCO for natural resource damages (NRD). The Denver and Adams County jointly applied for NRD funds to purchase and restore the Heron Pond expansion property. Among other things, NRD funds can be used to acquire property that will remain undeveloped and to restore the property’s natural resources.

The Wastewater Management Division of the Denver Public Works Department,

along with the Adams County Public Works Department and with the assistance of the Urban Drainage, will be responsible for designing, constructing, and maintaining the stormwater detention facilities on the Heron Pond expansion portions of the Natural Area. Denver Wastewater Management, with assistance from UDFCD, will be responsible for designing, constructing, and maintaining the stormwater detention facilities on the Heron Pond portion of the Natural Area. Denver Wastewater

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Management will be responsible for completing the construction of and managing the 2-3 acre constructed wetlands portion of the Natural Area. Denver will have the responsibility of restoring and maintaining the Natural Area except as noted above. Table 3 summarizes the sizes, ownership, and organizational responsibilities for the three parcels that comprise the Heron Pond Natural Area.

A key part of the project will be the restoration of land that is currently vacant with native plant and animal species that were found in similar physical environments prior to Euro-American settlement. The property will be used primarily as an urban natural area, with other uses permitted and managed such that they will not impair the natural values of the property. This project will provide limited opportunities for educational, scientific and passive recreational uses.

Threats to the Heron Pond Natural Area

The main threats to the Natural Area appear to be 1) proliferation of noxious weeds; 2) toxic materials that already exist in the sediment on the bottom of Heron Pond as well as potential toxic materials that may be contained in storm water runoff that will accumulate in the storm water detention facilities on the Heron Pond expansion property; 3) excessive visitor use that may adversely affect the local wildlife; 4) stray dogs that may harass wildlife; and 5) noises and visual intrusion by future adjacent land uses. Subsequent sections of this plan outline goals, objectives and actions that will abate these threats and create a significant natural area for Denver.

Vision for the Heron Pond Natural Area

The Heron Pond Natural Area will be an example of the historic South Platte River floodplain ecosystem and will serve as a sanctuary for wildlife and a place where people can experience and learn about nature. The Natural Area will also be a model for combining stormwater detention and the creation and restoration of wetland, riparian and upland plant communities in an urban setting. Goals for the Heron Pond Natural Area

The goals for the Heron Pond Natural Area are as follows: Goal 1 – Create and enhance natural wildlife habitat. Goal 2 – Detain stormwater runoff from the regional drainage basin, and use the stormwater to establish and sustain aquatic, wetland and riparian ecosystems. Goal 3 – Create and maintain an urban open space area. Goal 4 – Create and maintain passive recreation opportunities for school groups and for the general public.

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Objectives for the Heron Pond Natural Area

Objectives are statements that are specific, measurable, and achievable, with a deadline and a specified location. The following objectives provide a link between the goals above and the specific action steps below.

Objectives for goal 1 (natural wildlife habitat) Objective 1.1 - By December 31, 2000, there will be no more than an occasional stray pet or unauthorized human use of the Heron Pond Natural Area. Objective 1.2 - By December 31, 2000, create 2-3 acres of diverse emergent and rooted aquatic wetland along the new stormwater inlet channel adjacent to Northside Park. There will be at least 10 native wetland plant species present in the wetland and with a basal cover of all native wetland plant species combined of at least 50%. As used here, basal cover refers to the proportion of the water or substrate surface, whichever is higher in elevation, that is covered with living plants. Objective 1.3 – By December 31, 2001, temporarily restore the Heron Pond expansion property with native plant species as outlined in the Native Plant Community Restoration Plan appended to this Management Plan. The frequency of all native plant species combined will be least 70%, assuming a frequency quadrat of 12.5 cm x 25 cm, and the frequency of all noxious weed species combined will be less than 20%, assuming a frequency quadrat of 25 cm x 25 cm. In addition, for the portion of the expansion property that will not be subsequently disturbed by stormwater detention pond construction, there will be an average of at least 4 native perennial plant species per m2. Frequency and species richness measurements will exclude seedlings. Objective 1.4 – By December 31, 2001, reduce the abundance of each of the highest-priority noxious weed species in the Heron Pond Natural Area. Objectives for goal 2 (stormwater detention) Objective 2.1 – Dredge the existing Heron Pond stormwater detention facility if necessary. Objective 2.2 – Subject to budget availability, by December 31, 2004, expand the existing Heron Pond stormwater detention facility toward the western boundary of the Heron Pond parcel. Objective 2.3 – Subject to budget availability, by December 31, 2004, establish a new stormwater detention basin and an unlined stormwater conveyance ditch on the Heron Pond expansion parcel and connect it with the expanded Heron Pond. The new basin will accommodate 16-20 acre-feet of stormwater runoff for no more than seven days per runoff event, with the bottom of the basin being 2 feet above the mean surface elevation of Heron Pond and with the sides of the basin graded to a 4:1 slope or flatter so as to be

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continuously vegetated by native plant species. The detention ponds shall be planned, coordinated, constructed, and maintained using best management practices so as to minimize to the extent practical adverse environmental impacts to the Natural Area. Areas disturbed by construction will restored promptly in accordance with the Native Plant Community Restoration Plan that is appended to this Management Plan once construction activities are completed. Objective for goal 3 (urban open space) Objective 3.1 – By December 31, 2000, Denver will officially designate the Heron Pond Natural Area as a park. Objective 3.2 - By December 31, 2000, secure classification of the Heron Pond Natural Area as a “conservation and restoration area” within the Natural Areas program of the Denver Parks and Recreation Department. Objectives for goal 4 (passive recreation) Objective 4.1 – By August 31, 2001, create a wildlife viewing facility southeast of Heron Pond that will accommodate up to 30 people at one time. This facility will include a visitor structure, interpretive signage, and unpaved paths that connect the facility to the public parking area west of the National Guard Armory. The facility will be sited and designed so it provides an interesting view of the surface of Heron Pond. The wildlife viewing facility will be designed and constructed in such a way that visitors will be discouraged from wandering on to the rest of the Natural Area. The viewing facility will be screened from surrounding commercial and industrial areas by the artful placing of native plant species that are included in the Native Plant Community Restoration Plan. Objective 4.2 – By July 1, 2000, post signs explaining the prohibitions against recreating on or fishing in Heron Pond. Management Policies

Obviously, this plan cannot deal with every possible situation that will arise in the future at the Heron Pond Natural Area. The purpose of these management policies is to provide general guidance to natural area and stormwater detention facility managers. Policy 1 – Human use of the Heron Pond Natural Area will be concentrated in the wildlife viewing area in the southeast corner of the Natural Area to minimize adverse effects of dispersed human use. Policy 2 – Active recreational activities such as ball games, soccer, and frisbee will not be allowed. Facilities for these activities will exist at the adjacent Northside Park. Policy 3 – Fishing, swimming or boating on Heron Pond is prohibited due to public safety considerations and to minimize impacts on wildlife. Boat access will be allowed as needed to monitor contaminants in Heron Pond.

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Policy 4 – Once restoration is completed, removal or disturbance of native plants, animals or natural features is prohibited. This prohibition includes activities such as hunting, trapping, plant collecting, firewood collecting, cutting trees, and rock collecting. Exceptions may be made on a case-by-case basis as approved in advance in writing by the Manager, Denver Department of Parks and Recreation. This policy is not meant to prohibit prescribed burning, use of herbicides, mowing, cutting or grazing activities that are conducted to maintain native plant communities. Policy 5 – Motor vehicles will not be allowed except as required to support land management, stormwater detention pond maintenance, or emergency response activities. Policy 6 - The following activities are also prohibited: subdivision of land; accumulating or dumping of trash; and commercial or industrial uses including but not limited to signs, timber harvesting, and mining. Policy 7 - Pets are not permitted except at the wildlife viewing facility and on the access path that connects the viewing facility to the parking area at Northside Park. All pets must be leashed and under the direct control of a responsible person at all times. Policy 8 - Heron Pond shall continue to function as an urban stormwater detention facility owned and operated by Denver Public Works. The Wastewater Management Division of the Denver Public Works Department, in conjunction with Adams County Public Works and assisted by Urban Drainage, may periodically maintain the stormwater detention ponds and conveyance channels periodically to remove accumulated sediment. It is acknowledged that maintenance will entail the use of heavy equipment to dredge and clean the ponds and that this will cause temporary adverse environmental impacts to the ponds, conveyance channels and equipment access routes. These impacts, including loud noises, the removal of vegetation, and loss of wildlife habitat, are expected to be transitory and will be minimized by Denver Public Works using best management practices. Policy 9 - Agencies and organizations involved with the Heron Pond Natural Area shall notify and coordinate with other involved agencies and organizations and shall plan, schedule and perform their construction and maintenance activities so as to minimize adverse environmental impacts on the Natural Area. Involved agencies shall include as appropriate the Denver Department of Parks and Recreation, Denver Wastewater Management Division, Denver Environmental Services Division, Urban Drainage, Adams County Public Works Department, Colorado Department of Public Health and Environment, Colorado Division of Wildlife, and Colorado Open Lands. Policy 10 - All construction and maintenance of the stormwater detention facility (ponds, conveyance channels and access routes) at the Heron Pond Natural Area will be performed using best management practices recommended in the Urban Drainage and Flood Control District’s latest edition of the Urban storm Drainage Criteria Manual, Volume 3. Areas disturbed by construction and maintenance shall be restored promptly

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in accordance with the Native Plant Community Restoration Plan that is appended to this Management Plan once construction or maintenance activities are completed.

Actions Steps and Associated Calendar Years of Activity

The following actions needed to achieve the goal 1 (natural wildlife habitat) and its associated objectives:

a) Implement control measures for highest-priority weed species. (2000-2004) b) Remove junk and debris from the uplands and from Heron Pond. (2000) c) Seed the Heron Pond expansion parcel with the two recommended seed mixes. (2000) d) Fence the perimeter of the Natural Area as appropriate to control loose dogs and to

discourage human use of the Natural Area outside of the wildlife viewing area. (2000-2001)

e) Remove the chain-link fence that separates the Heron Pond expansion and Heron Pond expansion parcels. (2000)

Actions needed to achieve goal 2 (stormwater detention facility) and its objectives a) Design and construct a new stormwater conveyance / wetland channel and associated

wetlands on lands south of Heron Pond Natural Area that connects to the stormwater detention facility at Heron Pond. (1999-2000)

b) Remove or cover the existing concrete channel on lands south of Heron Pond Natural Area. (1999-2000)

c) Subject to budget availability, design and construct additional stormwater detention capacity on the western side of Heron Pond. (1999-2004)

d) Subject to budget availability, design and construct a stormwater detention facility on the Heron Pond expansion tract that incorporates target storage volume and detention times and meshes with the plant community restoration plan and connects with the stormwater conveyance channel and constructed wetland along the western side of Northside Park. Subject to budget availability, connect the new detention pond to the expanded Heron Pond. Retain the five mature cottonwood trees on the Heron Pond expansion tract if possible. (1999- 2004)

Actions needed to achieve goal 3 (urban open space) and associated objectives a) Pursue designation of Heron Pond Natural Area as an official Denver park. (2000) b) Propose inclusion of Heron Pond Natural Area as an official natural area classified as

“conservation and restoration”. (2000) c) Complete the Conservation Easement over the Heron Pond and 2-3 acre constructed

wetlands portions of the Natural Area. (2000)

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Actions needed to achieve goal 4 (passive recreation) and associated objectives a) Design the wildlife viewing area including visitor structure, interpretive exhibits and

access paths that connect to North Side Park. (1999-2000) b) Develop a landscaping plan for the visitor structure that features native plant species

found in the restored plant communities of the Natural Area. The landscaping plan will help create a natural setting and will screen the viewing area from surrounding commercial and industrial land uses. (1999-2000)

c) Construct wildlife viewing facilities. (2000-2001) d) Install landscaping. (2001)

References Alston, M. 1999. Coordinator, South Platte River Corridor Project, City and County of Denver, Denver, CO. Conservation with Alan Carpenter. Anonymous. 1999. Limited environmental investigation, Heller property. Unpublished report prepared by City and County of Denver, Department of Environmental Health, Environmental Services Division, Denver, CO. Anonymous. 1998a. ASARCO Globe Plant. Colorado Department of Public Health and Environment. Internet 10/20/98. Available:http://www.state.co.us/gov_dir/cdphe_dir/hm/rpglobe.html

Anonymous. 1998b. ASARCO, Inc., Globe Plant. Environmental Protection Agency. Internet 10/20/98. Available: http://www.epa.gov/region08/html/r80815.htm Anonymous. 1998c. Climate data for the city of Denver. Western Regional Climate Center. Internet 1/5/99. Available: http://wrcc.dri.edu Anonymous. 1995. Flood insurance map. Map No. 08001C0340 G. Effective date: August 16, 1995. National Flood Insurance Program, Federal Emergency Management Agency. Brecken, R., and R. Lentz. 1995. Colorado breeding bird proof listing for Commerce City Quadrangle, Q3910478. Colorado Bird Atlas, Denver, CO. Brune, R. 1998. A vegetation survey of the South Platte River at Denver. Unpublished report on file at Denver Audubon, Denver, CO. King, K. 1998. Conversation with Thomas Murray, October 20, 1998. Kingery, H. E. (editor). 1998. Colorado breeding bird atlas. Colorado Breeding Bird Atlas Partnership, Denver, CO. 636 pp.

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Kittel, G., R. Rondeau, and A. McMullen. 1996. A classification of the riparian vegetation of the Lower South Platte River and parts of the Upper Arkansas Basins, Colorado. Unpublished report prepared for the Colorado Department of Natural Resources and the U. S. Environmental Protection Agency. Lindvall, R.A. 1980. Geologic Map of the Commerce City quadrangle, Adams County, Colorado. U.S. Geological Survey, Geological Quadrangle Map GQ-1541.

Vargas-Madrid, V. 1999. District Wildlife Manager, Denver, CO. Conservation with Alan Carpenter. Weber, W. A. 1990. Colorado flora – eastern slope. University of Colorado Press, Niwot, CO.

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Table 1. Plant species observed at Heron Pond Natural Area on May 13, 1998, October 13, 1998, and May 13, 1999. Alien species are denoted by a single asterisk; alien species that are included on the State of Colorado noxious weed list are denoted by a double asterisk. The pound sign denotes species that are recommended for restoration. Nomenclature follows Weber (1990) with synonyms of more traditional names in parentheses. _____________________________________________________________________ Trees, shrubs and vines Chokecherry (Padus virginiana ssp. melanocarpa = Prunus virginiana ssp. melanocarpa) # Siberian elm = Chinese elm (Ulmus pumila) * Coyote willow (Salix exigua) # Golden currant (Ribes aureum) # Honey locust (Gleditsia triacanthos) * Peach-leaf willow (Salix amygdaloides) # Plains cottonwood (Populus deltoides ssp. monilifera) # Rubber rabbitbrush (Chrysothamnus nauseosus ssp. graveolens) # Russian olive (Elaeagnus angustifolia) * Woodbine (Parthenocissus inserta) # Herbaceous species Alyssum (Alyssum minus) * Aster (Machaeranthera canescens) Blue grama (Condrosium gracile = Bouteloua gracilis) # Bottlebrush squirreltail (Elymus elymoides = Sitanion hystrix) # Bulrush (Schoenplectus sp. = Scirpus sp.) # Canada thistle (Cirsium arvense) ** Cattail (Typha angustifolia) Cereal rye (Secale cereale) * Cheatgrass (Anisantha tectorum = Bromus tectorum) ** Cheeseweed (Malva neglecta) * Cowpen daisy (Xymenesia encelioides) * Daisy (Erigeron divergens) Dalmatian toadflax (Linaria genistifolia ssp. dalmatica) ** Diffuse knapweed (Acosta diffusa = Centaurea diffusa) ** Dock (Rumex sp.) Field bindweed (Convolvulus arvensis) ** Foxtail barley (Critesion jubatum = Hordeum jubatum) Giant ragweed (Ambrosia trifida) * Goat’s beard (Tragopogon dubius) * Gumweed (Grindelia squarosa) Hairy goldenaster (Heterotheca villosa) Jim Hill mustard (Sisymbrium altissimum) *

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Table 1. Continued Little bluestem (Schizachyrium scoparium) Milkweed (Asclepias sp.) Musk thistle (Carduus nutans) ** Needle-and-thread (Stipa comata) # Perennial pepperweed (Lepidium latifolium) ** Prickly lettuce (Lactuca seriola) * Puncture vine (Tribulus terrestris) ** Purple three-awn (Aristida purpurea) Ragweed (Ambrosia psilostachya) Ragwort (Senecio spartioides) Redstem filaree (Erodium cicutarium) * Russian thistle (Salsola australis) ** Sandberg bluegrass (Poa secunda) # Sand dropseed (Sporobolus cryptandrus) # Scarlet globemallow (Sphaeralcea coccinea) Scotch thistle (Onopordum acanthium) ** Side-oats grama (Bouteloua curtipendula) # Smooth brome (Bromopsis inermis = Bromus inermis) * Summer cypress (Kochia scoparia) ** Sunflower (Helianthus annuus) Tall wheatgrass (Lophopyrum elongatum = Agropyron elongatum) * Tansy mustard (Descurainia sophia) ** Western wheatgrass (Pascopyrum smithii = Agropyron smithii) # Yellow sweetclover (Melilotus officinalis) * ______________________________________________________________________

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Table 2. Breeding Bird Species Associated with Four Habitat Types Found at Heron Pond Natural Area. Species are from Kingery 1998. Number of blocks refers to the number of priority blocks in Colorado in which the respective bird species has been found. Species that were observed on May 13, 1998, October 13, 1998, and on May 13, 1999 are denoted with an asterisk. For emergent wetlands, L = landbird, S = shorebird, and W = water bird. _______________________________________________________________________ Lowland riparian Emergent wetlands No. of blocks Species No. of blocks Species 281 Bullock’s oriole* 478 Red-winged blackbird* (L) 225 Yellow warbler* 256 Mallard* (W) 207 Western kingbird 196 Killdeer (S) 197 Black-billed magpie* 161 Common snipe (S) 196 Northern flicker* 123 Yellow-headed blackbird (L) 186 Great horned owl 100 Common yellowthroat (L) 183 Mourning dove* 94 Sora (S) 177 House wren 87 Spotted sandpiper (S) 177 American robin 81 Green-winged teal (W) 159 Eastern kingbird 68 Cinnamon teal (W) 157 American kestrel 65 Song sparrow* (L) 146 Blue grosbeak 63 American coot (W) 146 Western wood-pewee 62 Blue-winged teal (W)

56 Brewer’s blackbird* (L) 50 Wilson’s phalarope (S) 43 American avocet (S)

40 Virginia rail (S) 37 Savannah sparrow (L) 29 Northern harrier (L) Open water, streams Open water, lakes No. of blocks Species No. of blocks Species 179 American dipper 322 Mallard* 179 Spotted sandpiper 128 Green-winged teal 142 Mallard* 114 Spotted sandpiper 83 Belted kingfisher* 58 Killdeer 53 Common merganser ______________________________________________________________________

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Table 3. Summary of sizes, ownership, and organizational responsibilities for the three parcels that comprise the Heron Pond Natural Area. Parcel

Size

Owned By

Designs and constructs stormwater detention facility

Manages stormwater detention facility

Manages park and natural area aspects of the parcels

Heron Pond 18 acres Denver Denver Wastewater Management Division, assisted by Urban Drainage and Flood Control District

Denver Wastewater Management Division

Denver Parks and Recreation (South Platte River District and Natural Areas Program)

Heron Pond Expansion (Heller tract)

25 acres Denver Denver Wastewater Management Division, Adams County Public Works, assisted by Urban Drainage and Flood Control District

Denver Wastewater Management Division and Adams County

Denver Parks and Recreation (South Platte River District and Natural Areas Program)

Stormwater inlet channel / constructed wetlands

2-3 acres Denver Denver Wastewater Management Division, assisted by Urban Drainage and Flood Control District

Denver Wastewater Management Division

Denver Parks and Recreation (South Platte River District and Natural Areas Program)

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20

21

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Appendices Appendix 1. Contacts List Appendix 2 Heron Pond Natural Area Designation Appendix 3 Aerial Photo of Site Appendix 4 Weed Management Plan Appendix 5. Native Plant Community Restoration Plan

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Appendix 1 – Contacts List

Marc Alston, Coordinator, South Platte River Corridor Project, DCM, 303 W. Colfax, Suite 1400, Denver, CO 80204; phone 720.913.8817 (before January 1,2000) Marc Alston, US Environmental Protection Agency, Region 8, Mail Code EPR-EP, 919-18th Street, Suite 500, Denver, CO 80202; phone 303. (after January 1, 2000) Fonda Apostolous, ASARCO remediation, Colorado Department of Public Health and Environment; phone 303.692.3411 Linda Baggus, Executive Director, Green City Project, 300 E. Hampden Avenue, Englewood, Co 80110; phone 303.761.6361; fax 303.761.6365 Banner Rebar Inc, 5353 Franklin St., Denver, CO 80216; phone 303.298.7822 Bill Bennerman, Department of Environmental Health, Division of Environmental Services, City and County of Denver, 1391 Speer Blvd., Suite 700, Denver, CO 80204; phone 303.285.4033; fax 303.285.5619 Ned Burke, Asset Management Office, City and County of Denver, 216 16th St. Mall, Suite 900, Denver, CO 80202; phone 303.640.2727 Alan Carpenter, Land Stewardship Consulting, Inc., 2941 20th St., Boulder, CO 80304; phone 303.443.8094; fax 303.449.9514 Bar Chadwick, Director, South Platte River Initiative, Office of the Mayor, City and County of Denver, 110 – 16th Street, Suite 400, Denver, CO 80202; phone 720. 913.5516; fax 720. 913.5599 Casey Davenhill, citizen member of Wildlife Task Force, Mayor’s South Platte River Commission; phone 303.744.0613 Crystal Gray, Director, Adams County Parks Department, 9755 Henderson Road, Brighton, CO 80601; phone 303.637-8005 Daren Duncan, Engineering Manager, Adams County Public Works Department, Development Building, 4955 East 74Th Avenue, Commerce City, CO 80022; phone 303.853.7114 Iron and Metals, Inc., 5555 Franklin St., Denver, CO 80216; phone 303.292.5555 Kristen King, contamination in Heron Pond; phone 303.692.3212

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Mike Kinsey, citizen member of Wildlife Task Force, Mayor’s South Platte River Commission; phone 303. 985-7252 Mike Muller, citizen member of Wildlife Task Force, Mayor’s South Platte River Commission; phone 303. Don Norris, history of Heron Pond; phone 303.446.3597 Myrna Poticha, citizen member of Wildlife Committee of the Mayor’s South Platte River Commission; phone 303. O.J. Watson Equipment 5335 Franklin St., Denver, CO 80216; phone 303.295.2885 Elizabeth Richardson, Public Affairs Manager, Colorado Open Lands, 274 Union Blvd., Suite 320, Lakewood, CO 80228; phone 303.988.2373; fax 303.988.2383 Lesley Roper, Park Superintendent, Platte River District, Department of Parks and Recreation, City and County of Denver, 945 S. Huron Street, Denver, CO 80223; phone 303.964.2583; fax 303.880.5501 Ben Urbonas, Chief, Master Planning & South Platte River Programs, Urban Drainage and Flood Control District, 2480 W. 26th Avenue, Suite 156-B, Denver, CO 80211; phone 303.455.6277; fax 303.455.7880 USA Waste Franklin St. Recycling Center, 5395 Franklin St., Denver, CO 80216; phone 303.296.4124 Vicki Vargas-Madrid, District Wildlife Manager, Colorado Division of Wildlife; phone 303.291.7137; fax 303.291.7114 Andrew Wallach, Deputy Director State Board of the Great Outdoors Colorado Trust Fund, 303 East 17th Avenue, Suite 900, Denver, CO 80203; phone 303.863.7522 Mark Walker, Voluntary Cleanup Coordinator, Colorado Department of Public Health and Environment, Mail Code HMWMD-RP-B2, 4300 Cherry Creek Drive South, Denver, CO 80246, phone 303.692-3449; fax 303.759.5355 Gayle Weinstein, City Naturalist, 8540 East Lowry Blvd., Building 1491, Denver, CO 80220; phone 303.341.0115

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Appendix 2

CITY AND COUNTY OF DENVER

DEPARTMENT OF PARKS – RECREATION | 201 W. COLFAX AVENUE | DENVER COLORADO 80202-5328

JOHN W. HICKENLOOPER Kim Bailey MAYOR Manager

City and County of Denver Denver Parks and Recreation

NA TURAL AREAS DESIGNA TION OF

HERON POND NATURAL AREA I. Findings

A. In accordance with Article VIII (Natural Areas) of Chapter 39 (Parks and Recreation) of the Denver Revised Municipal Code (“Natural Areas Ordinance”) and the Rules & Regulations for Natural Areas (“Natural Areas R&R’s”) adopted by the Manager of the Department of Parks and Recreation (“Manager”) on January 16, 2001, the Manager proposes to designate as a “natural area” the property to be known as the Heron Pond Natural Area, which includes Heron Pond site and an adjoining property known as the Heller Property, as depicted on the map attached as Exhibit A.

B. Said Heron Pond Natural Area is owned by the City and County of Denver and managed and operated by the Department of Parks and Recreation, subject to certain requirements, conditions, and restrictions identified in Finding G below.

C The proposal to designate Heron Pond as a natural area was initiated by the Natural Areas staff of the Department of Parks and Recreation (“Department”). The Department collected pertinent guidance information and consulted with the Natural Areas Advisory Committee of the Parks and Recreation Advisory Board, which recommended that Heron Pond Natural Area is appropriate for natural area designation.

D A draft Management Plan was developed in consultation with the Natural

Areas Advisory Committee. It was agreed that the draft Management Plan and the proposed natural designation process should be presented to the Parks and Recreation Advisory Board for consideration through a public review process.

E. In preparation for the public review process before the Parks and Recreation

Advisory Board, public notification was provided as follows:

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1. The Heron Pond Natural Area was posted, at a publicly conspicuous location, with a sign no less than 42 inches by 30 inches for no less than 45 days prior to the public review meeting. Said sign informed the public of the proposed natural area designation and the date, time and place of the public review meeting.

2. All pertinent registered neighborhood organizations, city council members, and parties expressing an interest in this natural area designation were likewise timely notified of the public review meeting by mail or personal delivery and provided with a summary of the draft Management Plan.

F. The public review meeting was held on July 12, 2001 and oral and written comments on the proposed natural area designation andlor draft Management Plan were received by the Parks and Recreation Advisory Board.

G. Following review public comments and consideration of the draft or amended Management Plan, the Parks and Recreation Advisory Board authorized at a meeting of the Board on September 13, 2001, that a written recommendation be delivered to the Manager that the natural area designation of Heron Pond Natural Area was warranted, that the Management Plan be approved, and the following conditions be included in its recommendation:

1) The Heron Pond site is subject to a Deed of Conservation Easement recorded at reception number 2003190098, September 8, 2003, in the Denver Clerk and Recorder’s Office, and the Heller Property is subject to a Declaration of Covenants, Conditions and Restrictions, recorded at reception number C06 18052, December 1, 1999, in the Adams County Clerk and Recorder’s Office (collectively, the “Documents”). Any natural area designation shall be subject to the requirements, conditions, and restrictions contained in the Documents.

2) The development, approval, and implementation of a Management Plan was a requirement of the Documents, and said Management Plan has been prepared and approved in accordance with the Documents. Said Management Plan will be the same Management Plan as required for natural area designation and may only be altered in the manner provided by the Documents.

3) The Heron Pond Natural Area is part of a stormwater detention facility and may be subject to expansion, dredging, and other maintenance and improvements as specified in the Documents.

4) The Heron Pond Natural Area has certain environmental contamination issues that may need to be addressed in future years as specified in the Documents.

G. The Manager finds that Heron Pond Natural Area satisfies all four criteria under the Natural Areas R&R’ s, namely, that Heron Pond Natural Area:

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1) Provides or could provide protection for a sustainable natural ecosystem, wildlife habitat, native plant species and communities, geological formations, or water corridors or wetlands;

2) Serves as an example of a rare or unique native condition in an urban setting in need of ecological preservation;

3) Serves as an outdoor classroom or laboratory for scientific study or other educational opportunities for the public; and

4) Functions as an area of biological diversity, natural beauty, and inspiration which meets aesthetic needs and which enriches the meaning and enjoyment of human life.

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II. Conclusion & Decision

1. Having reviewed the written recommendation of the Parks and Recreation

Advisory Board, the Manager accepts the recommendation and conditions of the Board and the Management Plan as presented.

2. The Manager hereby designates the Heron Pond Natural Area, as described in

Exhibit A, as a natural area, with the classification as a “Conservation and Restoration Area,” as provided in the Natural Areas R&R’s.

3. This designation shall be subject to the four conditions specified by the Parks

and Recreation Advisory Board and restated in Finding G above. 4. The Management Plan is approved and is incorporated herein as part of the

natural area designation. A copy of said Management Plan is attached as Exhibit B. The Management Plan may not be amended or altered except as provided in the Documents identified in Finding G.

5. Rules and Regulations enforceable in the Heron Pond Natural Area shall be as

provided in Section VI of the Natural Areas R&R’s. The Heron Pond Natural Area shall be posted with signs and other notification systems that inform the public of restrictions on access and use of the natural area, in accordance with Section VI of the Natural Areas R&R’s.

6. The Heron Pond Natural Area shall henceforth be included in the Department’s

Natural Areas Program under the direction of the City Naturalist, who will provide the expertise for the ongoing restoration, management, and protection of the Heron Pond Natural Area.

This natural area designation is effective this 18th day of October, 2005.

_________________________________ Kim Bailey Manager of Parks and Recreation _________________________________ Judith Montero Council District 9

Appendix 3

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Appendix 4

Weed Management Plan for the Heron Pond Natural Area 1. INTRODUCTION A. Context of Weed Management

There has been a tremendous expansion of invasive alien species across the US, including Colorado. New problem weed species arrive in Colorado every year. Weeds create large economic losses for agriculture in both cropland and rangeland situations. Noxious weeds often provide poorer habitat for wildlife than native vegetation. Proliferation of alien plant species alters ecosystem processes and threatens certain native species with extirpation. Thus, unchecked weeds threaten our economic livelihood and our biological heritage. In recognition of the economic and ecological impacts of weeds, the General Assembly of the State of Colorado passed the Colorado Weed Management Act, also known as the Colorado Noxious Weed Act, in 1996. The act requires landowners and managers to manage noxious weeds if they are likely to damage neighboring lands. This act provides that each county in Colorado shall adopt a noxious weed management plan for the unincorporated portions of the county. Weeds are rapidly becoming one of the most pressing issues for natural managers. Unfortunately, most natural areas contain many alien plant species. In the vast majority of cases, there is not enough labor and money to control all the species of weeds that occur in a natural area. Thus, managers are forced to choose which weed species they will control and which they will not, at least initially.

B. Overview of Approach to Weed Management

Weed control is part of property management. This plan is based on restoration, maintenance, and the improvement of desired plant species and associations, rather than on simply eliminating weeds. Preventative programs will be implemented to keep the management area free of species that are not yet established at Heron Pond but which are known to be pests elsewhere in the area. Priorities are set to reduce or eradicate weeds that are already established on the Natural Area, according to their actual and potential impacts on the land management goals for the property, and according to the ability to control them now versus later. Actions will be taken only when careful consideration indicates leaving the weeds unchecked would result in more damage than controlling it with best available methods. The plan follows the adaptive management approach. First, weed species are identified through inventory of the property and by gathering information from other sources. Second, land management goals and weed management objectives

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are established and recorded for the property. Third, priorities are assigned to the weed species and weed patches based on the severity of their impacts, while considering the ability to control them. Fourth, methods are considered for controlling them or otherwise diminishing their impacts and, if necessary, re-order priorities based on likely impacts of weed control actions on target and non-target species. Fifth, Integrated Weed Management (IWM) plans are developed for the highest-priority weed species based on this information. Sixth, the IWM plans are implemented. Seventh, the results of management actions are monitored and evaluated in light of weed management objectives for the Natural Area. Finally, this information is used to modify and improve weed management objectives, control priorities, IWM plans, thereby starting the cycle again. The premise behind this weed management plan is that a structured, logical approach to weed management, based on the best available information, is cheaper and more effective in the long run than an ad-hoc approach where one deals with weed problems one at a time as the arise

2. DESCRIPTION OF THE HERON POND NATURAL AREA A. Boundaries

The Natural Area is located in the City and County of Denver and Adams County, Colorado. The property is found on the Commerce City USGS 7 ½ minute quadrangle map, in the northwest ¼ of section 14, township 3 south, range 68 west of the 6th principal meridian. The entire Heron Pond Natural Area (the existing 18-acre Heron Pond, the 25-acre Heron Pond expansion tract, plus 2-3 acres of constructed wetlands) will consist of approximately 46 acres of deeded ground. The northern boundary of the property is delineated by 54th Avenue. The western boundary is delineated by Washington Street except in the northwest corner where the property abuts the Corvette Connection (5380 Washington St.), a shop that specializes in customizing Corvette automobiles, and except for a strip farther south along Washington Street. The southern boundary is delineated by a chain link fence which abuts an empty industrial site owned by Denver and the 13.4-acre Northside Park which is currently under construction. The eastern boundary abuts three businesses: USA Waste of Colorado, a solid waste recycling plant; Planet Rebar, a steel fabrication plant; and O.J. Watson Equipment, a truck conversion and customization shop.

B. Resource Base Conservation Values, Purpose and Benefits of the Heron Pond Natural Area

The conservation values of the Heron Pond Natural Area are natural, scenic, open space, wildlife habitat, and passive recreation. These conservation values apply to all current and future parcels that will comprise the Natural Area.

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The overall purpose of the Heron Pond project is to create an urban natural area that contains a stormwater detention facility. The property will be used primarily as an urban natural area, with other uses permitted and managed such that they do not substantially impair the current and restored natural values of the property. As used here, an urban natural is an area that is dominated by native plant communities and associated native wildlife species supported to the greatest extent by ecological processes; is located in a densely populated area; and is managed to mitigate adverse effects associated with a dense human presence. The Heron Pond Natural Area will provide a number of benefits for the citizens of Denver and Adams County. These include 1) habitat and buffer land for aquatic, wetland, and riparian wildlife species such as invertebrates, amphibians, songbirds, waterfowl and small mammals; 2) native wetland, riparian and upland plant communities and species, including potentially the prairie gentian (Eustoma grandiflora) which is rare in Colorado; 3) limited opportunities for recreation such as a wildlife viewing area that would complement the active recreational amenity that will be provided by the future Northside Park which abuts the south side of the Natural Area; 4) limited opportunities for passive recreational and educational uses; and 5) detention of stormwater and to trap sediments flowing from the local drainage basin. As the vision for the Heron Pond Natural Area contained in the Management Plant indicates, there is great potential to restore an example of the historic South Platte River floodplain at the site. Therefore, a key component of the Heron Pond project will be the restoration of land that is currently vacant with native plant communities and animal species that were found in similar environments in the South Platte River floodplain prior to Euro-American settlement.

Vegetation

Currently there is a narrow riparian area dominated by trees along the edge of heron Pond. The dominant trees are plains cottonwood (Populus deltoides ssp. monilifera), and Siberian elm (Ulmus pumila). Coyote willow (Salix exigua), which is a shrub, also occurs in patches around the pond margin. A few Russian olive shrubs (Elaeagnus angustifolia) are also present. Plains cottonwood and peach-leaf willow are common, desirable, native species that are indigenous to wetland and riparian habitats along the South Platte River. Siberian elm and Russian olive are invasive, alien species. Cattail (Typha angustifolia) is present in the pond itself, mostly in the shallow areas at the inlet and in the northwest corner of the pond. The native upland shrub, rubber rabbitbrush (Chrysothamnus nauseosus ssp. graveolens) is present in small numbers near the pond. Ground-layer vegetation on the uplands surrounding the pond consists mostly of alien weeds. The most common include summer cypress (Kochia scoparia), Russian thistle (Salsola australis), field bindweed (Convovulus arvensis), diffuse

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knapweed (Acosta diffusa), cheatgrass ( Anisantha tectorum), musk thistle (Carduus nutans), Canada thistle (Cirsium arvense), scotch thistle (Onopordum acanthium), yellow sweetclover (Melilotus officinalis) and tansy mustard (Descurania sophia). Desirable, native ground layer plant species that are present in small amounts on the uplands surrounding the pond include sand dropseed (Sporobolus cryptandrus), western wheatgrass (Pascopyrum smithii), needle-and-thread (Stipa comata), purple three-awn (Aristida purpurea), side-oats grama (Bouteloua curtipendula) and aster (Machaeranthera sp.). Additionally, there are five mature cottonwood trees on the Heron Pond expansion property. These trees are supported by storm water that collects around the trees. An effort should be made to preserve these cottonwoods and promote the establishment of new cottonwoods on this part of the property.

Wildlife

Due to the close proximity of the South Platte River, the property is part of a wildlife corridor along the river. Some of the wildlife species that are known to use the South Platte River corridor and surrounding habitat area include mule deer (Odocoileus hemionus), coyote (Canus latrans), red fox (Vulpes vulpes), raccoon (Procylon lotor), skunk (Mephitis mephitus), porcupine (Eriethizon dorsatum), beaver (Cartor canadensis), muskrat (Ondatra zibethicus), Nutthall’s cottontail (Sylvilagus nuttallii), and black-tailed prairie dog (Cynomys ludovicianus) (Vicki Vargus-Madrid, Colorado Division of Wildlife). Red foxes have been observed at Heron Pond by various people. Mule deer (Odocoileus hemonius) is the only principal big game species in the area. The Colorado Museum of Natural History sponsors the Breeding Bird Atlas program (Kingery 1998). Under the auspices of this program, volunteers have surveyed birds in a priority block in the southeastern corner of each US Geological Survey 7½ minute quadrangle map in Colorado. A priority block is a rectangle which is 3 miles (north-south) by 3½ miles (east-west) or one-sixth of a quadrangle. The Natural Area does not fall within a priority block. However, data are available for the Commerce City quadrangle in which the property is located. The Breeding Bird Atlas data indicate the bird species that one might expect to inhabit the property. In the Commerce City quadrangle priority block, 52 species were recorded as observed (20), possible (7), Probable (4), and confirmed (21) in 1995 (Breckon and Lentz 1995). This list of bird species for the Commerce City quadrangle is found in Appendix 3 of the Heron Pond Management Plan (Carpenter and Murray 1999). One of the main conservation values of the Heron Pond Natural Area is habitat for waterfowl. The Breeding Bird Atlas includes the “Open Water Lakes”, “Open Water Streams”, “Emergent Wetlands Marshes”, and “Lowland Riparian” habitats

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in its surveys (Kingery 1998). Bird Species that are associated with these habitats in Colorado are listed in Table 2 of the management plan. During our visits on May 13, 1998, October 13, 1998, May 13, 1999, and October 20, 1999, we observed several species of birds. These include double-crested cormorant, kingfisher, Canada goose, mallard, pintail, black-crowned night heron, white pelican, great-blue heron, kestrel, black-billed magpie, American avocet, mourning dove, American robin, northern (red-shafted) flicker, barn swallow, red-winged blackbird, Brewer’s blackbird, brown-headed cowbird, black-billed magpie, Bullock’s oriole, yellow warbler, chipping sparrow and song sparrow. Heron Pond contains a population of carp (Cyprinus carpio), an alien fish species. Flesh samples collected from carp from Heron Pond have been tested and determined to contain arsenic and mercury (Kirsten King, pers.comm). Therefore, fishing will be prohibited at Heron Pond.

Local Land Use

The Heron Pond Natural Area is located west of the South Platte River in the Globeville neighborhood at the northern edge of the City of Denver. The Natural Area is located in an urban setting that is characterized by various industrial and commercial uses. Adjacent properties include the former city of Denver municipal sewage treatment facility (now demolished), USA Waste of Colorado, Banner Rebar, OJ Watson Equipment, Iron and Metals Inc., the National Guards Armory, an unoccupied light industrial building, vacant land, and the ASARCO Globe Smelter. Also, the Heron Pond Natural Area will abut Northside Park which is currently under development. The southeast boundary of the Heron Pond Natural Area will abut the 13.4-acre Northside Park. The park lies atop Denver’s now demolished municipal wastewater treatment facility. This park will contain a soccer field, playground equipment, a picnic area, and other amenities. The Heron Pond Natural Area along with the adjacent Northside Park are important parts of the South Platte River Corridor project.

Threats to the Heron Pond Natural Area The main threats to the Natural Area appear to be 1) proliferation of noxious weeds; 2) toxic materials and sediments contained in storm water runoff that will accumulate in the storm water detention facilities on the Heller property; 3) excessive visitor use that may adversely effect the local wildlife; 4) stray dogs that harass wildlife; and 5) noises and visual intrusion by future adjacent land uses.

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3. INVENTORY OF WEED SPECIES A. Inventory of Weed Species Method of inventory

When we conducted an inventory on May 13th 1999, we divided the property into two sections. The first section included Heron Pond and the land immediately adjacent to the Pond. This section was searched by walking around the perimeter of the pond. The second section contained the remainder of the property (the Heron Pond expansion tract). This section was searched by walking the perimeter (fence line) and then walking across the Heller tract in parallel lines approximately fifty feet apart. The 2-3 acre constructed wetland parcel was not inventoried because construction activities were underway. Species that were targeted for inventory included diffuse knapweed, field bindweed, cheatgrass, Russian thistle, summer cypress, Dalmation toadflax, and Siberian elm. Alien plant species found on Heron Pond Natural Area (5/13/98, 10/13/98, 5/13/99) Asterisks denote species that are listed as noxious in Colorado. Alyssum (Alyssum minus) Canada thistle* (Cirsium arvense) Cheatgrass* (Anisantha tectorum = Bromus tectorum) Cereal rye (Secale cereale) Cheeseweed (Malva neglecta) Chinese elm (Ulmus pumila) Cowpen daisy (Xymenesia enceloides) Dalmation toadflax* (Linaria genistifolia ssp. dalmatica) Diffuse knapweed* (Acosta diffusa = Centaurea diffusa) Giant ragweed (Ambrosia trifida) Field bindweed* (Convolvulus arvensis) Goatsbeard (Tragopogon dubius) Honey locust (Gleditsia triacanthos) Jim Hill mustard (Sisymbrium altissimum) Musk thistle* (Carduus nutans) Perennial pepperweed* (Lepidium latifolium) Prickly lettuce (Latuca seriola) Puncturevine* (Tribulus terrestris) Redstem filaree* (Erodium cicutarium) Russin olive (Elaeagnus angustifolia) Russian thistle* (Salsola australis) Scotch thistle* (Onopordum acanthium) Smooth brome (Bromopsis inermis = Bromus inermis) Summer cypress* (Kochia scoparia)

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Tall wheatgrass (Lophopyrum elongatum = Agropyron elongatum) Tansy mustard* (Descurania sophia) Yellow sweetclover (Melilotus officinalis)

B. Maps of Weed Infestations

We prepared maps for the weed species that are the highest priority for control (see Section 5.C below). In addition, we prepared maps for cheatgrass and summer cypress because of their high abundance in the Natural Area. Weed species maps are located in Figures A4-2 through A4-9.

4. MANAGEMENT GOALS AND WEED MANAGEMENT OBJECTIVES FOR THE PROPERTY

A. Land Management Goals Goals are statements that generally describe the conditions one is trying to create on a management area, not just things related to weeds. Goals generally deal with human values, natural resources and financial resources. The goals for the Heron Pond Natural Area are as follows: Goal 1 – Restore examples of native plant communities that were components of historic South Platte River floodplain ecosystems and adjacent drier areas in the Denver area.

Goal 2 – Detain stormwater runoff from the regional drainage basin, and use the stormwater to establish and sustain aquatic, wetland and riparian ecosystems at Heron Pond. Goal 3 – Provide a semi-natural setting in which people can view wildlife and learn about the ecology of the South Platte River floodplain ecosystem. Goal 4 – Manage the Heron Pond Natural Area such that it meets the criteria for the “conservation and restoration areas” classification within the Natural Area program of the Denver Parks and Recreation Department.

B. Weed Management Objectives

Objectives are statements that are specific, measurable, achievable, have a deadline and specify a location. They provide a link between very general goal statements and specific action steps. 1. Eradicate any new infestations of noxious weed species (plant species on Colorado State list) not currently found at Heron Pond Natural Area within one month of their discovery or before they set seed, whichever comes first.

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2. Eradicate by the end of the calendar year 2000 all alien weed infestations where the total area of the infestation(s) at Heron Pond Natural Area is less than 100 square feet (e.g. a patch 10 feet x 10 feet). As used here, eradication does not include seeds in the soil, but does include aerial stems, roots and rhizomes.

3. Reduce the abundance of each of the eleven highest-priority weed species (see Section 5.B) at Heron Pond Natural Area over the next five years.

5. PRIORITIES FOR WEED MANAGEMENT

A. Prevention

Preventing new weed species from becoming established at Heron Pond is the top priority. The most important thing that can be done to manage weeds at Heron Pond Natural Area is to prevent them from becoming established in the first place. The old adage that “an ounce of prevention is worth a pound of cure” certainly applies to weed management.

The establishment of healthy native plant associations on the Heron Pond Natural Area will help reduce the threat of alien plant invasion. However, due to the condition of the property prior to its restoration there may be a significant weed seed bank present in the soil. Consequently, weeds will be controlled especially diligently until the restored plant associations are established. See the Native Plant Community Restoration Plan in Appendix 5 for a discussion of how the proposed restoration will help prevent noxious weed establishment.

B. Weed Infestation Priorities

The location of a weed infestation is also very important. The highest-priority weed patches are those that are small and isolated from larger infestations of the same high-priority weed species and which occur on or could affect the conservation values of the Natural Area.

C. Weed Species Priorities

Weed management priorities based on the actual or potential threat that weeds pose to the management goals for the property. Two factors are used to set priorities, namely the weed species and the locations of weed infestations. Weeds species are important to consider because they vary considerably in the threat they pose to the conservation values of the property. In addition, weed species vary greatly in their susceptibility to control measures. Weed species that pose the greatest threat to achieving the management goals for the property and that need to be controlled immediately are the highest priority for management.

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Priorities were determined for the species that are listed as State noxious weeds or pose a significant threat to the land management goals for the Natural Area. In this plan, weeds are prioritized using the Hiebert ranking system (Hiebert and Stubbendiek 1993) and the results are shown in Table A4-1. The results were then plotted on a graph (Figure A4-1). Finally, we compared the results of the ranking system with the land management goals of the property to determine the highest-priority weed species for the Heron Pond Natural Area The following is a list of the highest-priority weeds for the Heron Pond Natural Area and the reasons for their selection as highest-priority species. Two letter abbreviations match those used in Figure A4-1.

Canada Thistle (CT) – spreads rapidly, only a few small patches present. Chinese Elm (CE) - relatively easy to control, removal is part of restoration program. Dalmation Toadflax (DT) - spreads rapidly, found in one small patch on the property. Diffuse Knapweed (DK) - spreads rapidly, found in moderate amounts throughout the property. Field Bindweed (FB) - hard to control, highest impact species, abundant on property. Honey Locust (HL) – relatively easy to control, several small trees present. Musk Thistle (MT) - few plants present, relatively easy to control. Perennial Pepperweed (PP) - spreads rapidly, found in three small patches.

Russian Olive (RO) - relatively easy to control, removal is part of restoration program, few are present.

Scotch Thistle (ST) - spreads rapidly, found in small amounts throughout the property. Smooth Brome (SB) - spreads rapidly, found in a few small patches.

6. WEED MANAGEMENT ACTIONS

A. Prevention Best management practices are designed to prevent weeds from establishing and

becoming a problem in the first place. Prevention measures that will be undertaken on the property are listed in Table A4-2.

Table A4-2. Recommended Prevention Measures Task Prevention Measure

1 Assign a Denver Parks staff person responsible for controlling weeds at Heron Pond. This person will learn how to identify highest-priority weed species in the field so he/she can spot them while doing weed control or other land management activities.

2 Resurvey the entire Heron Pond Natural Area annually for weeds. Be sure

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to inspect access roads, parking areas, paths and / or trails, ditch banks, the sides of ponds, and the perimeter of the property.

3 Implement the native plant community restoration plan to help prevent new infestations.

4

Once the restoration is under way, inspect heavy equipment for weed seeds

before it enters the property; the surrounding area is highly infested with weeds and any equipment that is used on neighboring properties should be cleaned before it is used at Heron Pond.

5 Place signs at the wildlife viewing area at Heron Pond to educate the public / visitors to the dangers of weeds and how they can avoid spreading them.

B. Weed control

Integrated Weed Management (IWM) is a process by which one selects and applies a combination of management techniques (biological, chemical, mechanical, and cultural) that, together, will control a particular weed species or infestation efficiently and effectively. The underlying concept behind the IWM approach is that two or more control actions will hopefully interact to provide a greater level of control than a simple combination. In other words, one plus one equals three. IWM does not necessarily require the eradication of a weed species or a particular infestation of weeds, although these might be objectives in some cases. IWM is both species specific, tailored to exploit the weaknesses of a particular weed species, and site specific, tailored to be practical and safe. The Heron Pond Natural Area is small enough to be patrolled and treated on foot in one or two days. Many weed species can be controlled through a combination of tilling, pulling / cutting, and spot herbicide treatment. Table A4-3 provides recommended control actions for the highest-priority weed species at Heron Pond Natural Area. Control actions were generated by: First, reviewing the land management goals and weed management objectives for the Natural Area; Second, reviewing control section of the species abstract for each of the highest-priority weed species; Third, choosing the control method that best fits the weed management objectives without interfering with the land management goals for the Natural Area. If a single control method can be used to control several weed species (e.g. mowing), that method will be more efficient than using a different control method for every weed species.

7. MONITORING

Monitoring is the repeated collection and analysis of information to evaluate progress in meeting resource management objectives. Monitoring is worth doing because it is cheaper over time to adjust weed management actions periodically based on what is learned about their effectiveness than to follow the same course

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of action indefinitely. Without some type of monitoring, one will not be able to know if weed management objectives are being met. And if one’s objectives are not being met, the weed management actions probably need to be altered to be successful.

Monitoring will be conducted in two ways. First, every year the property will be searched in the same manner as the original inventory. Weeds and patches of weeds will be marked on a map, the sizes of the patches estimated and compared to prior maps of weed infestations. One can thus determine if weed patches disappear, shrink or if new patches appear. If infestations of new noxious weeds are found on the property, they will be treated promptly. Second, the monitoring of the native plant community restoration areas will provide quantitative information about noxious weeds. Read the Native Plant Community Restoration Plan, Appendix 5 of the Heron Pond Management Plan for details.

8. REFERENCES Carpenter, A.T. and T.A. Murray. 1999. Management plan for the Heron Pond Natural Area.

Carpenter, A.T. and T.A. Murray. 2000. Creating an integrated weed management plan: a handbook or owners and manager of lands with natural values. Caring for the Land Series Volume IV. Colorado Natural Areas Program, Department of Natural Resources, Denver CO.

Hiebert, R.D. and J. Stubbendiek. 1993. Handbook for ranking exotic plants for management and control. National Park Service, Natural Resources Report NPS/NRMWRO/NRR-93/08.

Kingery, H.E. (editor). 1998. Colorado breeding bird atlas. Colorado Breeding Bird Atlas Partnership, Denver, CO. 636 pp.

Vargus-Madrid, V. 1998. List of common animal species in Adams County. Colorado Division of Wildlife, Denver, CO.

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Table A4-3. Recommended Integrated Weed Management control actions for the highest-priority weed species at Heron Pond Natural Area. Highest-priority weed species

Control Actions

Canada thistle Cut all stems in patches three times annually; in the early fall, about four weeks after the third cutting, treat resprouts with glyphosate either with a spray or wick. Repeat procedure every year until patch is eradicated.

Chinese elm Cut trunks as close to the ground as possible; best done in September- October; within 30 seconds of cutting, apply triclopyr herbicide to cut stump concentrating herbicide on outer portion of stump; check for resprouts the following May – June and cut/apply herbicide to resprouts.

Dalmation toadflax

Pull, or dig up stems with as much of the root system as possible; dispose in dumpster if flowers or fruits are present; follow up inspection in 4-8 weeks, pull any resprouts.

Diffuse knapweed

Around Heron Pond, pull or dig all plants after bolting but before seeds mature; follow up inspection in 4-8 weeks, pull or dig any resprouts; The following spring/early summer (during the early flowering stage), treat any emerging plants with glyphosate; follow up inspection in 2-4 weeks, pull or spray any surviving plants; Repeat this cycle for as long as knapweed is present. On Heron Pond expansion tract, see recommendation for weed control in Native Plant Community Restoration Plan in Appendix 5.

Field bindweed

See recommendation for weed control in Native Plant Community Restoration Plan in Appendix 5.

Honey locust Cut trunks as close to the ground as possible; best done in September- October; within 30 seconds of cutting, apply triclopyr herbicide to cut stump concentrating herbicide on outer portion of stump; check for resprouts the following May – June and cut/apply herbicide to resprouts.

Musk thistle Cut seed heads after flowering but before seeds are shed; dispose of seed heads in dumpster; repeat annually as long as plants with seed heads appear.

Perennial pepperweed

Cut all stems in late May; cut all stems again after 4 weeks; spray resprouted stems with glyphosate + isopropyl amine salt of 2,4-D at the flower bud stage after the second cutting.

Russian olive Cut trunks as close to the ground as possible; best done in September- October; within 30 seconds of cutting, apply triclopyr herbicide to cut stump concentrating herbicide on outer portion of stump; check for resprouts the following May – June and cut/apply herbicide to resprouts.

Scotch thistle Cut all stems after flower heads appear but before seeds fall; dispose in dumpster; follow up inspection in 4-8 weeks, cut or spray any resprouts with metsulfuron or chlorsufuron (if the patch is away from standing water or shallow groundwater); dig up rosettes or spray rosettes with clopyralid, dicamba, picloram, or 2,4-D.

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Smooth brome Dig up the patches of smooth brome before seed head maturation; follow up inspection in 4-8 weeks; dig up any new shoots. Repeat this process annually to control any resprouts and to deplete the soil seed bank.

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Canada Thistle [Cirsium arvense (L.) Scop.]

Other Common Names: creeping thistle, Californian thistle

Keys to Identification: • Purple flowers form in clusters of

1-5 per branch. • The floral bracts of Canada thistle

are spineless. • Stems occur in colonies, arising

from horizontal roots.

Description: Canada thistle is a colony-forming, perennial herb of the Sunflower (Asteraceae) family. Adult plants range from 2-4 feet in height. Leaves are spiny, alternate, oblong or lance-shaped, with the base leaves stalkless and clasping, or extended down along the stem. Flower heads are purple and borne in clusters of 1-5 per branch. Seeds are straw or light brown in color, straight or slightly curved (Moore 1975). Canada thistle has two types of roots, horizontal and vertical. The horizontal roots produce numerous shoots, while vertical roots store water and nutrients in their many small branches. Impacts: Canada thistle is an aggressive, creeping, perennial weed. It infests crops, pastures, rangelands, roadsides, ditch banks, and riparian areas (Beck 1996). Canada thistle spreads rapidly through horizontal roots, which give rise to shoots (Moore 1975). Its root system can be extensive, growing horizontally as much as 18 feet in one season (Nuzzo 1998). Most Canada thistle patches spread at a rate of 3-6 feet/year. By asexual reproduction, it is possible that a colony of male plants would produce no fruits, but still maintain itself and spread by creeping (Whitson et al. 1996). Habitat: Canada thistle is found throughout the northern half of the United States and lower portions of Canada. It thrives in the Northern Temperature Zone due to its day length response and a high temperature limitation on growth (Haderlie et al. 1991). In Colorado, Canada thistle is typically found from 4,000-9,500 ft along roadsides, fields, pastures, meadows, and other disturbed areas (Anonymous 1,2). Although Canada thistle mainly invades disturbed areas, it does invade native plant communities in riparian areas, open meadows (including wetlands), and ponderosa pine savanna (Anonymous 2). Canada thistle is adapted to a wide range of soil types and environmental conditions (Anonymous 1). It is best adapted to rich, heavy loam, clay loam, and sandy loam, with an optimum soil depth of 20 inches (Anonymous 1,2). Canada thistle can tolerate saline soils (up to 2% salt) and wet or dry soil (Anonymous 2). However, it does not tolerate waterlogged or poorly aerated soils. Canada thistle usually occurs in 17-35 inch annual precipitation zones or where supplemental soil moisture is available (Beck 1996). it is commonly found in riparian areas and along ditch banks. Stewardship Summary: Canada thistle is a very tenacious weed and can be hard to manage once it is established. If left uncontrolled, Canada thistle can quickly spread over a large area and crowd out desirable species. Control efforts should target Canada thistle plants in high-quality areas first (typically areas that contain mostly native species and few undesirable species), and then work on controlling lower quality areas (areas that are already infested with undesirable species and have less desirable species present).

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Management strategies should be adjusted to reflect weather conditions (Nuzzo 1998). For example, drought stress reduces the effectiveness of most herbicides, but increases the effectiveness of mechanical controls (e.g., mowing or burning).

It takes at least two years of control to determine whether a particular method is effective. Several studies have recorded a temporary decline in Canada thistle in the first year of control followed by a return to the pre-treatment conditions the second growing season (Nuzzo 1998). Biology/Ecology: Over-wintering roots develop new underground roots and shoots in January and begin to elongate in February (Nuzzo 1998). Shoots emerge between March and May, when mean weekly temperatures reach 5° C, and form rosettes (Nuzzo 1998). Early in the spring, plants remain near the soil surface until long days (over 14 hours of light) trigger flowering and stem elongation (Haderlie et al. 1991, Anonymous 1). Canada thistle is imperfectly dioecious (male and female flowers are usually produced on separate plants). Female flowers can be readily distinguished from male flowers by the absence of pollen (abundant in male flowers) and presence of a distinct vanilla-like fragrance. Flowering occurs from June to October in Colorado (Anonymous 2). Seeds mature July to October and are distributed by wind. A female Canada thistle plant can produce up to 5,200 seeds in a season, but the average is about 1,500 seeds/plant (Anonymous 2). Mature seeds germinate most readily in mid-spring. Seeds that do not germinate may remain dormant for several years but most studies indicate that the majority of seeds do not remain viable after three years of burial (Anonymous 2). Seeds are readily transported by running water in streams and ditches (Morishita 1999).

Canada thistle reproduces primarily vegetatively through creeping horizontal roots, and can quickly form dense stands. Every piece of the root system is capable of forming a new plant (Anonymous 2). This allows dense monocultures of Canada thistle to form even without seed production. Canada thistle growth is limited or stopped when temperatures exceed 30° C for extended periods of time. Canada thistle is also shade intolerant. It can grow along the edge of forested areas, but is rarely found within forests.

Keys to Control: • Eliminate seed production. • Reduce the plant’s nutrient

reserves through frequent mowing or grazing followed by fall treatment with herbicide, and later re-seeding if needed.

Control: In general, Canada thistle is able to recover rapidly from most stresses by using stored energy from its roots. It can survive grubbing once or twice a month for many years befroe its root reserves are depleted (Sheley et al. 1995). The key to controlling perennials like Canada thistle is to stress the plant to reduce the nutrient reserves in the roots (Beck 1996).

Single herbicide applications do not provide long-term control due to problems in killing Canada thistle’s root system. Thus, multiple applications are required (Morishita 1999). Chemical control of Canada thistle should be conducted in the spring or fall depending on local environmental conditions. In general, fall treatments are more effective as herbicide absorption is enhanced in the late summer and fall when

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shoot to root translocation is the greatest. However, translocation of the herbicide is dependent on moist soil conditions. If fall is a dry period in your area, a spring application around the flower bud stage (early June), when root carbohydrate reserves are at their lowest, is recommended.

An integrated control strategy for Canada thistle was developed by Beck and

Sebastian (1993). First, begin mowing when Canada thistle is 12-15 inches tall and repeat at about one month intervals. The performance of Curtail can be improved when proceeded by two or three mowings (Beck 1996). Apply Curtail in October or about one month after the last mowing. Curtail is a mixture of clopyralid + 2,4-D. Clopyralid alone can be applied at a rate of 2/3 to 1 pint/acre in the spring or fall. Spring applications should be timed to the rosette to bud growth stages. Curtail should either be applied in the late spring (when Canada thistle plants are entering the bud growth stage) or in the fall (October) when Canada thistle roots are actively growing.

2,4-D or picloram are effective when applied at a rate of 1 lb. ai/acre in the spring when Canada thistle is in the pre-bud to early bud growth stages (about 10-15 inches tall). For increased control, retreat with dicamba (1 lb. ai/acre) in the fall to the regrowth.

Currently, there is no single biological control agent that effectively controls Canada thistle. However, there are several agents that have been reported to provide very limited control. One species, Urophora cardui (a gall fly), may be available for redistribution from the Division of Plant Industry’s Biological Pest Control Section.

Mowing pastures and hay meadows can be an effective control if it is repeated at about 2-4 week intervals throughout the growing season (Morishita 1999). Livestock grazing can act like mowing to reduce top-growth of Canada thistle, especially in the spring when the plants are tender. Cattle will readily graze Canada thistle later in the summer if it is sprayed with a dilute molasses solution. Combining mowing with herbicides will further enhance control of Canada thistle. Works Cited:

Anonymous (1). 1998. Botanical and ecological characteristics of Cirsium arvense. Forest Service Fire Effects Information System. Internet 07/28/98. Available: http://www.fs.fed.us/database/feis/

Anonymous (2). 1998. An assessment of exotic plant species of Rocky Mountain National Park, Cirsium arvense L. USGS Northern Prairie Wildlife Research Center. Internet 07/28/98. Available: http://www.npwrc.usgs.gov/resource/othrdata/explant/

Beck, G.K. 1996. Natural resources series, Canada thistle. Colorado State University Cooperative Extension. Internet 11/6/98: Availble:http://co.jefferson.co.us/dpt/openspac/weed/canthstl.htm Beck, K.G. and J.R. Sebastian. 1993. An integrated Canada thistle management system combining mowing with fall-applied herbicides. West. Soc. Weed Sci. 46:102-104.

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Haderlie, L.C., R.S. McAllister, R.H. Hoefer, P.W. Leino and L.F.James (Ed.). 1991. Noxious Range Weeds. Boulder: Westview Press. pp. 260-263.

Moore, R.J. 1975. The biology of Canadian weeds. 13. Cirsium arvense (L.) Scop. Canadian Journal of Plant Science. 55:1033-1048. Morishita, D. 1999. Canada thistle. In: R.L. Sheley and J.K. Petroff (eds.). Biology and management of noxious reangeland weeds. Oregon State University Press, Corvallis. pp.162-174.

Nuzzo, V. 1998. Element stewardship abstract for Cirsium arvense. The Nature Conservancy. Internet 10/16/98. Available: http://tnc.weeds.ucdavis.edu/esadocs.html Sheley, R.C., B.H. Mullin and P.K. Ray. 1995. Managing riparian weeds. Rangelands 17:154-157.

Whitson, T.D. Ed. 1996. Canada thistle. Weeds of the West. Western Society of Weed Science. Jackson: Pioneer of Jackson Hole. pg 109.

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Dalmation Toadflax (Linaria dalmatica (L.) Miller; Linaria genistifolia ssp. dalmatica (L.) Marie

and Petitmengin) Other Common Names: broad-leaved toadflax, wild snapdragon

Keys to Identification: • Dalmation toadflax can be

easily identified by its bright-yellow, snapdragon-shaped, flowers.

• Dalmation toadflax can be distinguished from yellow toadflax by its larger flowers and more ovate leaves (rather than the linear, somewhat pointed leaves that are characteristic of yellow toadflax).

Description: Dalmation toadflax is a perennial herb of the Sunflower (Asteraceae) family. Mature plants are up to three feet tall. A toadflax plant contains from 1-25 vertical, floral stems. These floral stems are thick-walled and somewhat woody. Leaves are broad, ovate to ovate-lanceolate, and are alternate, generally clasping but crowded. Flowers are born in loose, elongate, terminal racemes. Flowers are bright yellow and resemble snapdragons. Dalmation toadflax produces egg-shaped to nearly round capsulate fruits. Seeds are sharply angular, and slightly winged. The taproot may penetrate one meter into the soil. Horizontal roots may grow to be several meters long, and can develop adventitious buds that may form independent plants. Impacts: Dalmation toadflax is a persistent, aggressive invader and capable of forming colonies through adventitious buds from creeping root systems. These colonies can push out native grasses and other perennials, thereby altering the species composition of natural communities. Low-till cultivation practices have contributed to the resurgence of toadflax populations on agricultural lands (McClay 1992). New infestations of Dalmation toadflax can occur in naturally occurring disturbances or in small openings in pristine or excellent-condition rangeland (Lajeunesse 1999).

Dalmation toadflax contains a glucoside, a quinoline alkaloid, and peganine which make it toxic to livestock (Rees et al. 1996). However, dalmation toadflax is generally considered unpalatable, and reports of livestock poisonings are rare. Habitat: Both species of toadflax can adapt their growth to fit a wide range of environmental conditions, and have a tolerance for low temperatures and coarse-textured soils. In Colorado, dalmation toadflax is commonly found between 5,000 to 6,500 feet in oak, aspen, sagebrush, mountain brush, and riparian communities. Stewardship Summary: Dalmation toadflax can rapidly colonize open sites. It is most commonly found along roadsides, fences, rangelands, croplands, clear cuts, and pastures. Disturbed or cultivated ground is a prime candidate for colonization. Toadflax can significantly reduce crop yields and stress native communities. In one study, toadflax-free plots produced 2.5 times more grass than plots where toadflax was present (Robocker 1974).

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The seedlings of toadflax are considered ineffective competitors for soil moisture with established perennials and winter annuals (Morishita 1991). However, once established both species of toadflax suppress other vegetation mainly by intense competition for limited soil water. Mature plants are particularly competitive with winter annuals and shallow-rooted perennials (Robocker 1974).

Successful control can be obtained by pulling, or killing the plants with herbicide before toadflax seed production begins (Carpenter and Murray 1998). Since the plant also spreads through vegetative propagation, and the seeds can remain dormant for up to ten years, this process must be repeated every year for at least ten years to completely remove a stand. Competitive perennial grasses and forbs should be planted to utilize water and nutrients that would otherwise be readily available to toadflax. Biology/Ecology: Spring emergence occurs about mid-April and depends primarily on temperature. During the first year the plant forms a rosette and develops a deep root system. Prostrate stems emerge in September and produce ovate leaves. Prostrate stems are tolerant to freezing and are associated with floral stem production the following year (Robocker 1974). The strong upright floral stems that characterize mature toadflax plants develop after a winter’s dormancy, and emerge about the same time as new seedlings in mid-April. A single plant will produce from 1-25 floral stems. Flowering occurs from May-August and seeds mature from July-September. A mature dalmatian toadflax can produce up to 500,000 seeds annually (Morishita 1991). These seeds may remain viable in the soil for up to ten years.

Dalmation toadflax can reproduce vegetatively. Stems develop from adventitious buds on primary and lateral roots. Vegetative reproduction from root buds can occur as early as 2-3 weeks after germination, and is possible from root fragments as short as 1 cm in length (Zimmerman 1996). These buds can grow their own root and shoot systems, and become independent plants the next year. In addition to promoting growth, the large, deep, root systems of dalmation toadflax exploit water efficiently. The taproot may penetrate 3-4 feet into the soil and lateral roots may be 6-12 feet long.

Keys to Control: • Maintain a dense cover of

vigorous perennial plants. • Picloram, dicamba, and glyphosate

are effective when applied during flowering.

• Hand pulling is effective for small areas, especially in sandy soils.

Control: Management of Dalmation toadflax needs to focus on both reducing the rate of vegetative spread and reducing seed production (Lajeunesse 1999). Successful management requires integrating as many control tactics as possible. Dalmation toadflax has high genetic variabilty, and local populations can respond differently to control actions, especially herbicide treatments.

Herbicides have highly variable effects on Dalmation toadflax, probably due to its high genetic variability. Fall applications of picloram 0.5-1.0 lb. ai/acre has provided excellent control for one year. However, the higher concentrations of picloram may be injurious to desirable plants, plus picloram has been ineffective on some sites. A tank

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mix of picloram + 2,4-D controlled over 90% of Dalmation toadflax when applied pre-bloom or in the fall.

A six-year study found that phenoxypropionic herbicides such as diclorprop were more effective at controlling toadflax than phenoxyacetic herbicides such as 2,4-D (Robocker 1968). 2,4-D, MCPA, MCPB, and mecoprop used alone do not control toadflax.

Cutting or removal of the above ground portion of toadflax plants reduces the current year growth, but it will not kill the plant. Cutting toadflax stands in spring or early summer is an effective way to eliminate plant reproduction through seed production and dispersal. However, the long dormancy of toadflax seeds requires that the process be repeated annually for up to ten years. Sheep can help suppress Dalmation taodflax infestations and reduce seed production. The sheep showed no ill effects from eating toadflax and showed good weight gain (Lajeunesse 1999).

Hand pulling toadflax before seed set each year can be an effective control method. The hand pulling experiment on the Nature Conservancy’s Magnusson Butte Preserve in Washington showed that toadflax can be significantly reduced by pulling once a year as long as new seed is eliminated. Once again, this method must be repeated annually for up to ten years to completely remove a stand. The Division of Plant Industry’s Biological Pest Control Section currently has one species, Calophasia lunula, that may be available for redistribution on dalmation toadflax infestations. C. lunula larvae feed extensively on leaves and flowers of toadflax, severely damaging the plants.

Intensive clean cultivation techniques are recommended for successful toadflax control on agricultural land. Discing can be an effective method of toadflax control on agricultural lands. This method requires at least two years with eight to ten cultivations in the first year, and four to five cultivations the second year (Morishita 1991). Weed control should be accompanied by reseeding with a variety of plant species to occupy the site so as to prevent re-establishment of toadflax. An ideal mix of species would include cool- and warm-season plants as well as plants that root at a variety of depths. For example, shallow rooted, cool-season species such as sandberg bluegrass (Poa secunda) compete with toadflax seedlings. Works Cited: Carpenter, A.T. and T.A. Murray. 1998. Element Stewardship Abstract for Linaria dalmatica. The Nature Conservancy, Wildland Weed Program. Internet: 1/21/99. Available: http://tncweeds.ucdavis.edu/esadocs.html

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Lajeunesse, S. 1999. Dalmation and yellow toadfalx. In: R.L. Sheley and J.K. Petroff (eds.) Biology and management of noxious rangeland weeds. Oregon State Universtiy Press, Corvallis. pp. 202-216.

McClay, A.S. 1992. Effects of Brachypterolus pulicarius (L.) (Coleoptera: Nitidulidae) on flowering and seed production of common toadflax. The Canadian Entomologist 124: 631-636.

Moroshita, D.W. 1991. Dalmation toadflax, yellow toadflax, black henbane, and tansymustard: importance, distribution, and control. Pages 399-408 In: L.F. James, J.O. Evans, M.H. Ralphs, and R.D. Child (editors) Noxious range weeds. Westview Press, Boulder, San Francisco, and Oxford.

Robocker, W.C. 1974. Life history, ecology, and control of dalmation toadflax. Tech. Bull No. 79. Wash. Agric. Exp. Stn.

Zimmerman, J.A.C. 1996. Ecology and distribution of Linaria vulgaris (L.) Miller, Scrophulariaceae. USGS Biological Resources Division, Colorado Plateau Fielf Station-Flagstaff, Arizona. Internet. 01/14/98. Available: http://www.nbs.nau.edu/FNF/Vegetation/Exotics/linariatitle.html

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Diffuse Knapweed (Centaurea diffusa Lam.; Acosta diffusa (Lam.) Sojak)

Other Common Names: spreading knapweed, tumble knapweed

Keys to Identification: • The floral bracts have yellow

spines with teeth appearing as a comb along the spine margins.

• Flowers are usually white, but may be rose-purple to lavender in appearance.

• Seedlings have finely divided leaves that are covered with short hair.

Description: Diffuse knapweed is a biennial herb of the Sunflower (Asteraceae) family. Stems are upright, 4-24 inches tall, highly branched, angled, with short, stiff hairs on the angles. There are two types of leaves, basal (found at the base) and stem. Basal leaves are stalked and divided into narrow, hairy segments. Stem leaves are smaller, alternate, less divided, stalkless, and become bract-like near the flower clusters. Flower heads are broadly urn-shaped, 0.6-0.8 inches tall, solitary or in clusters of 2-3 at the ends of the branches. Floral bracts are yellowish with a brownish margin, sometimes spotted, fringed on the sides, and terminating in a slender bristle or spine. The heads contain two types of flowers, ray flowers around the edges surrounding tubular disk flowers. The petals are white, rose-purple, to lavender. Seeds are light brown to black. Bristles are generally absent or a mere fringe. Impacts: Diffuse knapweed is a pioneer species that can quickly invade disturbed and undisturbed grassland, shrubland, and riparian communities. Once established, diffuse knapweed outcompetes and reduces the quantity of desirable native species such as perennial grasses. Diffuse knapweed contains allelopathic chemicals, which can suppress competitive plant growth and create single species stands (Watson and Renney 1974). The densities of these stands can range from 1-500 plants/m2. Habitat: Diffuse knapweed is found on plains, rangelands, and forested benchlands. It is generally found on light, dry, porous soils. Diffuse knapweed has been observed in elevations up to 7,000 feet (Zimmerman 1997). It prefers open habitats to shaded areas (Watson and Renney 1974). Diffuse knapweed is not common on cultivated lands or irrigated pasture because it cannot tolerate cultivation or excessive moisture (Watson and Renney 1974). Stewardship Summary: Diffuse knapweed suppresses other vegetation presumably by intense competition for limited soil water and allelopathy. Its spread through vegetated areas can be slowed by associated grasses that remove moisture and nutrients from the rooting zone of diffuse knapweed (Allred and Lee 1996). Other non-native species, such as crested wheatgrass (Agropyron cristatum) have been shown to stress, and inhibit, diffuse knapweed invasion by limiting available soil moisture during the critical seedling growth stage. Biology/Ecology: Diffuse knapweed plants first form low rosettes and may remain in this form for one to several years depending on environmental conditions. Diffuse knapweed plants that complete their juvenile growth by the fall overwinter as rosettes and bolt in

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early spring (Watson and Renney 1974). Diffuse knapweed plants that have not finished the juvenile stage by the end of fall remain as rosettes through the second year and bolt during the third year. Flower buds are formed in early June and flowering occurs in July and August (Watson and Renney 1974). Mature seeds are formed by mid-August (Watson and Renney 1974). A single diffuse knapweed plant can produce up to 18,000 seeds (Harris and Cranston 1979) and a stand of diffuse knapweed can produce up to 40,000 seeds per square meter (Watson and Renney 1974).

Seed dispersal for diffuse knapweed is mainly by wind (Watson and Renney 1974). When the seed capsule sways in the breeze or is disturbed, the seeds fall from the small opening in top of the flower head and are distributed around the parent plant (Watson and Renney 1974). However, most of the involucres remain closed until the plant dries up, breaks off at ground level and effectively becomes a tumble weed, allowing seeds to be individually dispersed over long distances (Zimmerman 1997). Diffuse knapweed stalks readily lodge under vehicles, expanding their long distance dispersal. Keys to Control:

• Eliminate seed production. • Stress the plants nutrient

reserves as well as the soil seed bank through persistent management.

• Re-seed infested area with desirable species.

Control: The most effective method of control for diffuse knapweed is to prevent its establishment. Areas that are adjacent to known patches of diffuse knapweed should be monitored two to three times a year (spring, summer, and fall) and any new rosettes should be destroyed. Established plants or stands of diffuse knapweed can be pulled or spot treated with picloram. Burning may be an effective means of controlling diffuse knapweed in areas where seasonal or occasional fires are part of the natural ecosystem (Zimmerman 1997).

Currently, biological control agents are available but the extent to which they effectively control diffuse knapweed populations is unknown. The Division of Plant Industry’s Biological Pest Control Section has five species that may be available for redistribution. These five species are Uphora affinis, Uphora quadrifasciata, Agapeta zoegana, Sphenoptera jugoslavica, Cyphocleonus achates.

In areas without abundant native perennials, burning has been shown to be an

effective control of diffuse knapweed with strong grass regrowth occurring on burned sites (Zimmerman 1997). A low-severity fire may only top-kill (not kill the root) diffuse knapweed, but a severe fire will probably kill the entire plant. Dry soil conditions associated with burns may discourage diffuse knapweed re-infestation as moisture is the limiting factor for diffuse knapweed seed germination. Re-seeding desirable species helps to prevent a re-infestation of diffuse knapweed or other exotic species.

Several herbicides are relatively effective at controlling diffuse knapweed. Picloram is the most widely recommended (Harris and Cranston 1979). Other effective herbicides include dicamba, 2,4-D, and glyphosate (Beck 1997, Youtie 1997, Watson and Renney 1974). To save money and reduce grass injury resulting from higher use rates of

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a single herbicide, several of these herbicides can be combined (Beck 1997). Tank-mixes of picloram and dicamba (0.25 to 0.5 lb./acre + 0.125 to 0.25 lb./acre), picloram plus 2,4-D (0.188 lb./acre + 1.0 lb./acre), and dicamba plus 2,4-D (0.5 lb./acre + 1.0 lb./acre) all control diffuse knapweed (Beck 1997). A backpack sprayer or a wick is recommended in small areas to minimize damage to non-target plants. Herbicides should either be applied before the mature plants set seed, or to rosettes in the fall, to maximize effectiveness.

Cutting, mowing, or removing the above ground portion of the plant, before seed set may be an effective way to reduce seed production, but it will not eliminate the infestation. When a diffuse knapweed plant has been cut, the rosette may live and re-bolt. Additionally, diffuse knapweed seeds can remain dormant for several years, requiring any cutting program to be repeated several times annually (spring, summer, and fall) in order to be effective.

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Works Cited:

Allred, K.W., and R.D. Lee. 1996. Knapweeds, starthistles, and basketflowers of New Mexico. Internet 01/20/98. Available: http://webnmsu.edu/~kallred/herbweb/he03005.htm

Beck, G. K. 1997. Natural resources series, diffuse knapweed. Colorado State University Cooperative Extension. Internet 05/05/98. Available: http://ozma.jefferson.co.us/dpt/openspac/weed/dfknapwd.htm

Fletcher, R.A., and A.J. Renney. 1963. A growth inhibitor found in Centaurea spp. Canadian Journal of Plant Science 43:475-481.

Harris, P., and R. Cranston. 1979. An economic evaluation of control methods for diffuse and spotted knapweed in western Canada. Canadian Journal of Plant Science 59:375-382. Niefoff, J. E-mail message-broadcast. Sent 9-12-97, 9:29 AM.

Schirman, R. 1981. Seed production and spring seedling establishment of diffuse and spotted knapweed. Journal of Range Management 34:45-47.

Watson, A.K., and A.J. Renney. 1974. The biology of Canadian weeds Centaurea diffusa and C. maculosa. Canadian Journal of Plant Science 54:687-701.

Youtie, B. 1997. Weed control as the first step in protecting and restoring native plant communities on northeast Oregon natural areas. Conservation and Management of Native Plants and Fungi. Native Plant Society of Oregon, Corvallis, Oregon. pages 78-82.

Zimmerman, J.A.C. 1997. Ecology and distribution of Centaurea diffusa Lam., Asteraceae. USGS Biological Resources Division , Colorado Plateau Field Station-Flagstaff, Arizona. Internet 02/16/98. Available: http://www.nbs.nau.edu/FNF/Vegetation/Exotics/diffusa/ diffusa.html

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Field Bindweed

(Convolvulus arvensis L.) Other Common Names: small-flowered morning glory, wild morning glory, perennial morning glory, creeping jenny. Keys to Identification:

• Leaves of field bindweed are shaped like arrowheads.

• Flowers are funnel-shaped, white to pink, and have two small bracts 1 inch below the flower base.

Description: Field bindweed is a creeping perennial herb of the Morning-glory (Convolvulaceae) family. Stems are prostrate, 1-4 ft long, often climbing or forming dense mats. Leaves are alternate, simple, glaborous to finely pubescent, more or less arrowhead-shaped. Flowers are white to pink, borne singularly or in pairs on long stalks from the axils of the leaves with two bracts. Seeds are ovoid to pearl-shaped, three-angled with one rounded and two flattened sides. Seeds are dull, brownish-gray, and coarsely roughened. The roots system and rhizomes are extensive, whitish, cord-like, and fleshy. The primary root is a taproot from which lateral roots develop (Peterson 1998). Impacts: Field bindweed can be a serious threat to native plant communities because it has such a great capacity for regeneration (Peterson 1998). Detached roots and rhizomes have the potential to produce large numbers of new shoots. Both a high rate of seed production, and long-term viability allow the plant to spread and persist. Field bindweed’s broad range of environmental tolerances make it highly competitive in most areas. Habitat: Field bindweed occurs, and is competitive on, disturbed ground that is rich in introduced species. Field bindweed cannot tolerate shade and uses its viney stems to move into sunlight. Therefore, it is unlikely that field bindweed persists in later stages of community succession (Anonymous 1). Field bindweed is commonly found on more basic (rather than acidic) soil types and those of heavier texture. It can persist in dry to moderately moist soils, and is capable of surviving drought (Anonymous 2). Field bindweed may be found at altitudes as high as 10,000 feet (Whitson et al. 1996). Stewardship Summary: It is a native of Europe and was introduced in North America as early as the 1730s (Peterson 1998). Field bindweed can be a serious weed in native plant communities. Field bindweed requires active management once it is established because of its potential to regenerate rapidly. Even small infestations should be viewed as a serious threat and managed aggressively. It is also tolerant of a variety of environmental conditions which makes it highly competitive for resources (Anonymous 2). Biology/Ecology: The leaves of field bindweed vary greatly in size and shape with environmental factors such as light intensity, soil moisture, and with damage due to frequent cultivation. Flowers appear from June to September and occasionally until the first fall frost (Anonymous 2). The number of seeds produced per plant ranges from 25 to 300 and seed production is variable and depends on environmental conditions. Seeds

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have a hard impermeable seed coat. They generally fall near the parent plant but can be dispersed by water, as a contaminant in crop seeds, and by mammals and birds after ingestion. Field bindweed seeds can remain viable in the soil for over 20 years (Peterson 1998). Seeds mature within 2 weeks after pollination during hot summer days (Anonymous 1). Germination can occur in the fall or spring, over a wide range of temperatures (Anonymous 1).

Field bindweed overwinters by means of its roots and rhizomes. Shoots are killed back to the crown by freezing temperatures, but hardened roots can withstand temperatures as low as -6° C (Peterson 1998). Most lateral roots die back each year but some persist for several years, spreading horizontally (Peterson 1998). Buds arise on the lateral roots and develop into rhizomes that have the potential to establish new crowns when they reach the surface. Excised root segments establish new roots and crowns more effectively than rhizome segments (Peterson 1998).

Keys to Control: • Contain and persistently

control existing stands of field bindweed in order to exhaust the root system and deplete the soil seed bank.

• Maintain a healthy cover of perennial plants to discourage field bindweed establishment.

Control: Due to the vegetative reproductive ability of field bindweed, as well as the large seed bank of established populations, successful control requires repeated applications over several years. Chemical treatment often requires high rates as well as repeated applications. Successful treatment of bindweed can result in substantial damage to desirable plants. Foliar applications of glyphosate at 1.5 lb. ai/acre or picloram, dicamba, or 2,4-D at 1 lb. ai/acre can provide good control. Control is best when applied during early flowering and when soil moisture is low (Peterson 1998). Repeated applications are advised for long-term control.

Currently, there has been little evidence of a biological control agent that significantly damages or reduces populations of field bindweed. Two agents that are present in the U.S. and being studied are Aceria mahlerbae, a gall mite, and Tyta luctuosa, a moth (Rees et al. 1996).

Cutting, mowing, or pulling has a negligible effect unless plants are cut below the

surface in the early seedling stage. Well-established populations have a large seed bank in the soil that can remain viable for long periods of time (over 20 years). Works Cited:

Anonymous 1. 1998. Botanical and Ecological Characteristics, Convolvulus arvensis. Forest Service Fire Effects Information System. Internet 07/28/98. Available: http:// www.fs.fed.us/database/feis/plants/

Anonymous 2. 1998. An assessment of exotic plant species of Rocky Mountain National Park, Convolvulus arvensis L. (Convolvulus ambigens, Convolvulus incanens) field bindweed, morning glory (Convolvulaceae). USGS Northern Prairie Wildlife

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Research Center. Internet 07/28/98. Available: http:// www.npwrc.usgs.gov/resource/othrdata/explant/convarve.htm

Peterson, D.L. 1998. Element stewardship abstract for Convolvulus arvensis, field bindweed. The Nature Conservancy. Internet 11/08/98. Available: http://tncweeds .ucdavis.edu/esadocs.html

Rees, N.E., P.C. Quimby Jr., G.L. Piper, E.M. Coombs, C.E. Turner, N.R. Spencer, and L.V. Knutson (editors). 1996. Biological control of weeds in the west. Western Society of Weed Science in cooperation with USDA Agricultural Research Service, Montana Department of Agriculture, and Montana State University.

Whitson, T.D. Ed. 1996. Field bindweed. Weeds of the West. Western Society of

Weed Science. Jackson: Pioneer of Jackson Hole. pg 284.

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Musk Thistle [Carduus nutans L. subsp. macrolepsis (Peterman) Kazmi]

Other Common Names: nodding thistle

Keys to Identification: • Musk thistle can be

identified by the broad, spine-tipped bracts located under the flower.

• Flowering heads are terminal, solitary and usually nodding.

Description: Musk thistle is a biennial, or sometimes winter annual of the Sunflower (Asteraceae) family. Mature plants can grow as tall as 6 feet. It can appear solitarily or with several stems from one base, and is highly branched above. Leaves are dark green, deeply lobed, and spiny margined. The leaves extend onto the stem giving a winged appearance (Whitson et al. 1996). Basal rosettes are well developed, leaves elliptical to lanceolate, 6-14 inches, smooth to densely hairy. Flower heads are terminal, solitary, 1.5 to 3 inches in diameter, and usually nodding. Flowers are deep rose, violet or purple, occasionally white. Flowers are subtended by broad, spine-tipped bracts. Fruits are 0.2 inches long, shiny, yellowish-brown with a plume of white hair-like fibers. Seeds are oblong, brown, and have a tip (pappus) of numerous, whitish, barbed bristles. Impacts: Musk thistle is a highly competitive weed. It invades disturbed areas, pasture, rangeland, forest land, cropland, and waste areas throughout most of the United States. Musk thistle spreads rapidly and forms extensive stands, which force out desirable vegetation (Anonymous 2). Musk thistle may produce alleopathic chemicals that inhibit desirable plants beyond the spread of the rosettes (Wardle et al. 1993). Musk thistle seeds appear to remain viable for at least 10 years. Habitat: In Colorado, musk thistle is found up to approximately 10,000 feet in elevation (Beck 1999). Musk thistle does not appear to have any specific climatic requirements other than a cool period of vernalization for flowering (Anonymous 1). It occurs in areas with as little as 10 inches of annual precipitation (Anonymous 3). Musk thistle establishes best on bare soil, and small shallow cracks are ideal for seedling establishment (Anonymous 3). Musk thistle grows in all soil textures, but the soils must be well-drained (Anonymous 1). It occurs on soils with a pH range of 6.0 to 8.9 (Anonymous 1). Stewardship Summary: The key to managing musk thistle is to prevent seed production. Most control methods will have a detrimental effect on other plants and may cause a disturbance that will favor re-invasion by other exotic species (Anonymous 2). Dense musk thistle stands along roadsides and in degraded areas can be treated by spot use of herbicides, and in high-quality areas by a persistent program of pulling or cutting (Anonymous 2). Due to the long seed viability of musk thistle, up to 10 years, control methods may have to be repeated for many years to completely eliminate a stand. Biology/Ecology: Musk thistle reproduces solely by seed and is a prolific seed producer. Average productivity is approximately 10,000 seeds/plant, however, a single plant can produce up to 100,000 seeds (Beck 1999). Seeds germinate in the fall, forming a rosette

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of leaves. Typically, musk thistle over-winters as a rosette and bolts the following spring between April-June. Flowering begins in late May or early June and continues through mid-July (Anonymous 1). Seeds mature and are dispersed 1 to 3 weeks after flowering. Seed dispersal is by wind water, wildlife and livestock (Beck 1999). Seedlings establish only on bare soils and grow less when shaded by neighboring plants (Beck 1999). Keys to Control:

• Managing rangeland to minimize the amount of bare soil is essential to long-term control.

• Hand chopping at ground level just before flowering, or cutting and bagging seed heads before dispersal can be used to eliminate seed production.

• Repeated treatments over the course of several years can eliminate a musk thistle infestation.

Control: Musk thistle is most often controlled with herbicides. The most effective chemical control occurs when musk thistle is still in the rosette stage, and quickly decreases once the plant has bolted (Anonymous 1). 2,4-D, clopyralid, or dicamba at 1 lb. ai/acre are effective when applied 10-14 days prior to bolting. A combination of 2,4-D plus dicamba provided 97% control in an experiment in Minnesota (Anonymous 1). Fall applications of picloram at 1 lb. ai/acre to rosettes when other plants are dormant is often effective and has less impact on non-target species (Anonymous 1). Metsulfuron and chlorsulfuron are effective on bolted plants (Beck 1999).

Repeated mowing, hand pulling, or cutting can be used to stop the spread of musk

thistle. Mowing or hand-chopping after flowering, but before seed set, prevents seed development and dispersal (Heidel 1987). When pulling musk thistle, it is important to completely remove the crown so that the plant does not simply re-bolt and produce seeds. Repeated visits at weekly intervals over the 4-7 week flowering period is necessary because not all plants flower at the same time (Heidel 1987). Cut plants should be deeply buried or burned because seeds can mature and become viable after cutting (Anonymous 2). However, this weevil will attack native thistles, including rare species (Louda et al. 1997).

A number of insects have been used to help control musk thistle. The Division of

Plant Industry’s Biological Pest Control Section has two species, Rhinocyllus conicus, and Trichosirocalus horridus, that may be available for redistribution. The most widely released insect is the weevil Rhinocyllus conicus Froelich (Anonymous 1). In the spring, adults will feed on the leaves, mate, and deposit eggs on the bracts (Anonymous 1). When the eggs hatch the larvae begin to bore into the flowerhead, reducing the ability of the plants to produce viable seed. In some cases the weevil has reduced musk thistle populations to less than 10% pre-release levels (Anonymous 2).

One integrated approach to musk thistle management involves 1) managing livestock grazing to increase grass vigor and reduce bare ground; 2) spray rosettes with clopyralid or 2,4-D; 3) re-seed treated ground with competitive desirable plants in the fall after spraying; 4) follow-up with spot cutting of entire plants when first flowers appear annually for several years to deplete the seed bank in the soil.

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Works Cited:

Anonymous 1. Species abstracts of highly disruptive exotic plants at Pipestone National Monument, Carduus nutans. USGS Northern Prairie Wildlife Research Center. Internet 07/28/98. Available: http://www.npwrc.usgs.gov/resource/othrdata/exoticab/pipecard.htm

Anonymous 2. An assessment of exotic plant species of Rocky Mountain National Park, Carduus nutans. USGS Northern Prairie Wildlife Research Center. Internet 07/28/98. Available: http://www.npwrc.usgs.gov/resource/othrdata/explant/cardnut.htm

Anonymous 3. Biological and ecological characteristics, Carduus nutans. U.S. Forest Service Fire Effects Information System. Internet 07/28/98. Available: http://www.fs.fed.us/database/feis/

Beck, G. K. 1999. Biennial thistles. In: R.L. Sheley and J.K. Petroff (eds.) Biology and management of noxious rangeland weeds. Oregon State Universtiy Press, Corvallis. pp. 145-161.

Desrochers, A.M., J.F. Bain, and S.I. Warwick. 1988. The biology of Canadian weeds, Carduus nutans L. and Carduus acanthoides L. Canadian Journal of Plant Science 68: 1053-1068.

Heidel, B. 1987. Element Stewardship Abstract for Carduus nutans, musk thistle. The Nature Conservancy. Internet 7/30/98. Available: http://tncweeds.ucdavis.edu/esadocs/documnts/cardnut.html Louda, S.M., D. Kendall, J. Connor and D. Simberloff. 1997. Ecological effects of an insect introduced for the biological control of weeds. Science 277: 1088-1090. Wardle, D. A., K. S. Nicholson and A. Rahman. 1993. Influence of plant age on the allelopathic potential of nodding thislte (Cardus nutans) against pasture grasses and legumes. Weed Research 33:69-78.

Whitson, T.D. Ed. 1996. Musk thistle. Weeds of the West. Western Society of Weed Science. Jackson: Pioneer of Jackson Hole. p.76

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Perennial Pepperweed (Lepidium latifolium L)

Other Common Names: broad-leaved peppergrass, tall whitetop, Virginia pepperweed

Keys to Identification: • Perennial pepperweed has

dense clusters of white flowers that appear in early summer.

Description: Perennial pepperweed is a perennial forb of the Mustard (Brassicaceae) family. Mature plants are 1-3 feet tall. Under wet conditions plants can grow up to 8 feet tall. Leaves are lance-shaped, entire to toothed, bright-green to gray-green, and don’t have clasping bases (hoary cress leaves have clasping bases). The basal leaves are larger than the upper leaves. The white flowers are packed in dense clusters near the ends of branches. Fruits are nearly round, about 0.1 inch in diameter and usually sparsely hairy. The leaves and stems are covered with a waxy layer (Whitson et al. 1996). Impacts: Perennnial pepperweed is an aggressive colonizer of pastures and particularly riparian and wetland habitats. It establishes rapidly and can eliminate competing vegetation (Anonymous 1998). Deep-seated rootstocks make this weed difficult to control. The leaves and stems are covered with a waxy layer that makes this plant difficult to control with herbicides. Habitat: In Colorado, perennial pepperweed is found from 5,500 to 8,000 ft. Perennial pepperweed is most often found in open, unshaded areas on disturbed and often saline soils. It is locally common in riparian areas, marshy floodplains, valley bottoms, and seasonally wet areas. Perennial pepperweed is found in big sagebrush (Artemisia tridentata) communities of the Piceance Basin of Colorado (Anonymous 1998). Plant associates in these communities include twisted moss (Tortula ruralis) and desert goosefoot (Chenopodium pratericola) (Anonymous 1998). Stewardship Summary: Perennial pepperweed is an introduced forb of Eurasian origin that has established throughout the United States. It forms dense colonies by adventitious roots and deep-seated rhizomes. Perennial pepperweed is common in fields, wasteplaces, meadows, and along roadsides. It also invades irrigated pastures, cropland, and native meadows (Anonymous 1998).

Keys to Control: • Plants must not be allowed to

produce seed if control is to be successful.

• Use a combination of mechanical techniques and herbicide applications to control infestations.

Biology/Ecology: Perennial pepperweed reproduces mainly by spreading rhizomes, but can be aggressive colonizers of disturbed areas (Anonymous 1998). Dense flower clusters appear in early summer and continue through August. Perennial pepperweed produces an abundance of highly germinable seeds that have no apparent dormancy. However, Young (1999) has never collected a tall whitetop seedling in dense stands. Seedling establishment is not a significant problem once established tall whitetop plants are suppressed. He speculated that seed dispersal is important in long-distance dispersal.

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Control: The aerial portions of tall whitetop are easily killed by several herbicides, but it is very difficult to get enough herbicide to translocate to the roots and kill the numerous buds. (Young 1999). Tillage alone is ineffective because each small section of plant will produce new plants. However, tillage after herbicide applications may be an effective way to bring treated roots to the surface where they will dry out (Young 1999). Mowing (either mechanical or chemical) followed by spraying the resprouts with chlorsulfuron or glyphosate is very effective at controlling perennial pepperweed. Mowing twice in a growing season followed by chlorsulfuron treatment controlled more than 99% of pepperweed in California. Chemical mowing with 2,4-D at the flower bud stage followed by treatment of resprouts with glyphosate achieved 87% control (Renz and DiTomaso 1999). A combination of mechanical (cutting or pulling) and herbicide applications can provide effective control of perennial pepperweed. Plants should be cut or pulled during the flower bud stage. Herbicides should be applied to the recovering stems when they return to flower bud stage later the same year. Dicamba at 1 lb. ai/acre or glyphosate at 1.5 lb. ai/acre will control perennial pepperweed. Other herbicides that proved to be effective include chlorsulfuron, metasulfuron and imazapyr. Of these, chlorsulfuron and metasulfuron applied in the fall are most effective in a study in Colorado (Beck 1999). However, these herbicides cannot be used for weed control in the San Luis Valley of Colorado. Periodic mowing and spring burning have reduced perennial pepperweed density in Utah (Anonymous 1998). Works Cited:

Anonymous. 1998. Lepidium latifolium. Fire Effects Information System. U.S. Forest Service. Available 9/1/98. Internet: http://www.fs.fed.us/database/feis/plants/forb/leplat/distribution_and _occurrence.html. Beck, K.G. 1999. Perennial pepperweed and hoary cress in Colorado. Proc. National Whitetop Symposium, June 9-10, 1999. Alamosa, CO. pp. 19-22. Renz, M.J. and J.M. DiTomaso. 1999. Seasonal carbohydrate translocation patterns of perennial pepperweed (Lepidium latifolium) and implications for control in California. Proc. National Whitetop Symposium, June 9-10, 1999. Alamosa, CO. pp. 31-36. Young, J.A., C.E. Turner and L.F. James. 1995. Perennial pepperweed. Rangelands 17:121-123. Young, J.A. 1999. Lepidium latifolium L. biology and control. . Proc. National Whitetop Symposium, June 9-10, 1999. Alamosa, CO. pp. 3-4.

Whitson, T.D. Ed. 1996. Perennial Pepperweed. Weeds of the West. Western Society of Weed Science. Jackson: Pioneer of Jackson Hole. pg 230.

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1. Calweed Database. California Noxious Weed Control Projects Inventory. Internet 1/6/99. Available: http://endeavor.des.ucdavis.edu/weeds/

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Scotch Thistle (Onopordum acanthium L. and O. tauricum L)

Other Common Names: cotton thistle, winged thistle Keys to Identification:

• Scotch thistle can be identified from other thistles by the spiny wings attached to the stems and the dense, fine hair that give it a characteristic grayish-blue or blue-green color.

Description: Scotch thistle is a robust biennial forb of the Sunflower (Asteraceae) family. Mature plants can grow up to 12 feet tall, and have a large, fleshy taproot. Stems are numerous, branched, and have broad spiny wings. Leaves are large, irregularly lobed, and have sharp yellow spikes. Rosette leaves may be up to 2 feet long and 1 foot wide (Whitson et al. 1996). Upper and lower leaf surfaces are covered with a thick mat of cotton-like or woolly hairs, giving the foliage a gray-green color (Dewey 1991). Flower heads are numerous, 1-2 inches in diameter, with spine-tipped bracts. Flowers are violet to reddish. Impacts: Scotch thistle is an aggressive plant that is competitive with desirable native forage species. It can form dense stands that are impenetrable to livestock. Habitat: Scotch thistle is often found along roadsides, irrigation ditches, waste areas and on rangelands. It is especially fond of areas that are adjacent to riparian or sub-irrigated deeper soils along stream courses, lower alluvial slopes and bottomlands. It is increasing in densities throughout Colorado. Stewardship Summary: Scotch thistle is a native of Eurasia and is now sparsely naturalized over much of the United States. Onopordum acanthium is the predominant Scotch thistle species in the western United States and is characterized by its hairy leaves (Beck 1991). A hairless species, Onopordum tauricum, also occurs but much less frequently, mostly in the Arkansas River drainage in Colorado (Beck 1991). Biology/Ecology: Scotch thistle is a biennial that produces a large, ground level rosette the first year, and a tall, spiny plant the second. Flowering occurs from mid-June to September. Scotch thistle reproduces by seed with one plant producing 70-100 flowering heads containing 100-140 seeds per head (Young and Evans 1969). Seeds may remain viable in the soil for over 30 years. Control: Scotch thistle is best controlled in the rosette stage. Scotch thistle can be controlled by severing its taproot 1-2 inches below the ground. Control can be enhanced by a follow-up application of herbicides to the surviving rosettes.

Keys to Control: • Scotch thistle is best controlled in

the rosette stage. • Sever the taproot of Scotch thistle

1-2 inches below the ground. Picloram, dicamba, or 2,4-D at 1 lb. ai/acre, or a combination of dicamba and 2,4-D, are commonly used to control Scotch thistle. Herbicides should be applied in spring before Scotch thistle bolts or in the fall to rosettes (Beck 1991). Metsulfuron or chlorsulfuron are effective on Scotch thistle after bolting

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begins (Beck 1999). Herbicide rates will vary depending upon stand density and environmental conditions (Beck 1991).

One integrated approach to Scotch thistle management involves 1) managing livestock grazing to increase grass vigor and reduce bare ground; 2) spray rosettes with clopyralid or 2,4-D; 3) re-seed treated ground with competitive desirable plants in the fall after spraying; 4) follow-up with spot cutting of entire plants when first flowers appear annually for several years to deplete the seed bank in the soil. Works Cited: Beck, G. K. 1999. Biennial thistles. In: R.L. Sheley and J.K. Petroff (eds.) Biology and management of noxious rangeland weeds. Oregon State Universtiy Press, Corvallis. pp. 145-161.

Beck, G.K. L.F.James (Ed.). 1991. Biennial thistle control with herbicides. Noxious Range Weeds. Boulder: Westview Press. pp.254-259.

Dewey, S.A. L.F.James (Ed.). 1991. Weedy thistle of the western United States.

Noxious Range Weeds. Boulder: Westview Press. pp.247-253. Whitson, T.D. Ed. 1996. Scotch thistle. Weeds of the West. Western Society of

Weed Science. Jackson: Pioneer of Jackson Hole. pg 164. Young, J. A. and R. A. Evans. 1969. Germination and persistence of achenes of

Scotch thistle. Weed Science 20: 98-101.

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APPENDIX 5

Native Plant Community Restoration Plan for the Heron Pond Natural Area Introduction

The vision for the Heron Pond Natural Area is to recreate an example of the South Platte River floodplain as it likely existed prior to Euro-American settlement. However, most of the land that will be included in the Heron Pond Natural Area is vacant urban land that harbors an abundance of alien weeds and does not contain significant natural values, with the major exception of Heron Pond itself and its riparian fringe. Therefore, a major facet of the Heron Pond Natural Area project will be restoring wetlands, riparian areas, and uplands to approximate the vegetation that formerly existed in the floodplain along the South Platte River in what is now Denver. Within five years, the uplands west of Heron Pond will be transformed from weedy wasteland to a mosaic of attractive native plant communities and a wildlife sanctuary. Restoration will involve planting a number of plant species that inhabited the South Platte River floodplain in the past. The restoration will complement and be supported by the new stormwater detention basin that will be constructed on the Heron Pond expansion tract west of the existing Heron Pond. The detention basin will provide a portion of the water that will support the riparian plant communities that are targeted for restoration. Targets for Restoration As noted above, the Heron Pond Natural Area has been heavily modified by various human activities over the past 150 years. In addition, much of the land to be restored will be further modified in the process of constructing a stormwater detention pond on a portion of the Heron Pond expansion tract. As a result, there is some uncertainty at this time regarding exactly which plant associations, and therefore which plant species, will be appropriate for particular locations on the Heron Pond expansion tract. Nevertheless, there is no doubt that the South Platte River floodplain was included historically in the Plains Cottonwood (Populus deltoides ssp. monilifera) Alliance. An alliance is a unit of plant community classification that is determined by the dominant overstory plant species, here, plains cottonwood. Plant alliances are comprised of one or more plant associations that are recurring groups of plant species that occupy similar environments. Plant associations are determined by the dominant plant species in the overstory, mid-story and understory layers, respectively. For the purposes of the Heron Pond Natural Area restoration, we have chosen plant associations as the targets for restoration.

Along rivers such as the South Platte, different plant associations reflect primarily differences in soil moisture and disturbance history. Soil moisture is affected mostly by the elevation above the ground water table and also by soil texture. Drier sites are

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situated at higher elevations and wetter sites are situated at lower elevations. Disturbance is governed largely by the frequency and intensity of flooding and by land use practices.

Kittel et al. (1996) inventoried the riparian plant communities along the Lower South Platte River and parts of the Upper Arkansas River basins in Colorado. They identified five plant associations within the Plains Cottonwood alliance. Brune (1998) inventoried the plant associations along the South Platte River in Denver. He identified a number of associations, including a few that were dominated by native species and which might be appropriate models for Heron Pond. Using the plant communities that Kittel et al. (1996) and Brune (1998) identified, we propose six different target plant associations for different environments at the Heron Pond Natural Area (Table A5-1). We also propose one upland plant community for the reception area adjacent to the future stormwater detention pond where the material excavated to create the future detention pond will be deposited and (if needed) covered with a 1-foot thick cap of soil. We decided that the target plant community for the reception area is the Sand sagebrush/Sand bluestem Plant Community because the soil is likely to be very sandy and dry, similar to the soil in native sand sagebrush communities on the plains. Potential approximate locations of these restored plant associations at Heron Pond Natural Area are shown conceptually in Figure A5-1.

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Restoration Goal

The purpose of the restoration is to establish examples of the target native plant communities in the approximate locations shown in Figure A5-1 at the Heron Pond Natural Area. It would be convenient if previous research had determined with high certainty the “ideal” or “typical” plant species composition of each of these target plant communities; however, such is not the case. Given this situation, we propose that the goal for restoration is to establish native plant communities dominated by the plant species listed in this plan for each of the target plant communities and to have no more that a minor component of alien plant species in each community.

Denver has made a commitment to create about 4 acres of wetland on the Heron

Pond expansion parcel, pursuant to the “Proposal Natural Resource Damage Funds Adams County/City and County of Denver July, 1998”. The proposed restoration associated with the future stormwater detention pond is designed to meet this obligation. Restoration Objectives Objectives are specific, measurable statements that specify a place and a deadline and are achievable. The restoration objectives that follows are extracted from the Management Plan for the Heron Pond Natural Area. The first pertains to the 2-3 acres of created wetlands along the western side of Northside Park, and the second objective pertains to the temporary native plant community restoration at the Heron Pond expansion tract.

By December 31, 2001, create 2-3 acres of diverse emergent and rooted aquatic wetland along the new stormwater inlet channel adjacent to Northside Park. There will be at least 10 native wetland plant species present in the wetland and with a basal cover of all native wetland plant species combined of at least 50%. As used here, basal cover refers to the proportion of the water or substrate surface, whichever is higher in elevation, which is covered with living plants.

By December 31, 2001, temporarily restore the Heron Pond expansion property with native plant species as outlined in the Native Plant Community Restoration Plan appended to this Management Plan. The frequency of all native plant species combined will be least 70%, assuming a frequency quadrat of 12.5 cm x 25 cm, and the frequency of all noxious weed species combined will be less than 20%, assuming a frequency quadrat of 25 cm x 25 cm. In addition, for the portion of the expansion property that will not be subsequently disturbed by stormwater detention pond construction, there will be an average of at least 4 native perennial plant species per m2. Frequency and species richness measurements will exclude seedlings.

Plant Species Selected for Restoration

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The particular plant species selected for restoration were based on Kittel et al. (1996), Brune (1998) and Anonymous (1998). They identified plant species in vegetation samples in their study areas. We started with the native plant species found by Kittel at al. (1996) in sample stands for the respective plant associations. We then added additional native plant species suggested by Brune (1998) for the same or comparable plant associations. We also added or deleted certain plant species if we believed that these species would not be appropriate for particular areas at Heron Pond. For each of the seven environments that we anticipate will exist at the Heron Pond Natural Area once the stormwater detention pond is constructed, we have identified the target plant association and appropriate plant species for restoration of the seven respective plant associations (Tables A5-2 through A5-9). Note that we recommend a mixture of trees, shrubs, grasses and forbs (wildflowers) for planting for most of the plant associations. This variety reflects the hypothesized botanical diversity of the South Platte River floodplain and adjacent sandy uplands prior to Euro-American settlement. The resulting variety of plant species, seasons of growth (cool- and warm-season) and rooting patterns (shallow, medium-depth and deep rooting) will also help prevent establishment and spread of noxious weed species.

A major concern for the proposed restoration is the potential proliferation of

weeds, including noxious weed species. It is important to establish dense stands of native species quickly once the restoration begins; otherwise, the area will remain dominated by weeds. On the other hand, a portion of the Heron Pond expansion tract will be drastically disturbed in about 5-7 years when the new stormwater detention pond is constructed. Therefore, we propose that Denver establish a simple, temporary native plant community on the parts of the Heron Pond expansion property that will be disturbed during detention pond construction, and a permanent and more diverse native plant community on the parts that will not be disturbed by detention pond construction (Table A5-9). These species have a variety of seasonal growth and rooting patterns. We believe that both plant communities can compete successfully with weeds and greatly reduce the on-going management effort needed to control weeds. The recommended seed mixes contain only grasses to facilitate weed control after re-seeding. The potential weed control tools (sheep / goat grazing, mowing, prescribed burning, biological control agents, herbicide treatment) are much more effective for stands of pure grasses than they are for mixed stands of grasses, wildflowers, shrubs, and trees. Planting Stock and Densities

Tables A5-2 through A5-9 list recommended plant species for restoring the respective plant associations at Heron Pond. Plant materials for suggested restoration include balled-and-burlapped trees, 1-gallon shrubs, Super Cells, tubers, and seeds. The recommended planting rates for seeded species are deliberately high due to the tremendous quantities of weeds on the site. We recommend a higher than normal seeding rate to increase the likelihood of establishing a dense stand of native plant species (Velagala et al. 1997). Restoration Strategy

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Restoration will be most successful if it works with the successional process, focusing on manipulating seed safe-site availability, species availability and species performance (Jacobs et al. 1999). Manipulating seed safe-site availability involves preparing a suitable seedbed that is conducive to the germination of desirable species. Species availability is manipulated by selecting desirable, competitive native plant species for seeding and by suppressing the seed production of undesirable plant species, particularly noxious weeds. Manipulating species performance is accomplished by using tools such as livestock grazing, mowing, cutting, herbicides, biological control agents and prescribed burning to encourage or discourage the growth of particular plant species. Site Preparation and Initial Weed Control The Heron Pond expansion tract site currently has an abundance of noxious weeds, including field bindweed; diffuse knapweed, summer cypress, Russian thistle, and cheatgrass. Therefore, it is important to take steps to reduce the existing abundance of noxious weed species as well as the bank of weed seeds in the soil before seeds or transplants are planted. The goal of the temporary restoration is to create a weed-resistant native plant community that will suppress existing noxious weed species and prevent new noxious weed species from becoming established. Two alternative strategies to accomplish this goal are presented in Table A5-10.

Both strategies begin with efforts to suppress the most troublesome broad-leaf weeds (field bindweed and diffuse knapweed). We recommend a mixture of 1 pint of tordon + 1 quart of 2, 4-D per acre of infested ground sprayed on the Heron Pond expansion tract during the first week of May 2000. Next, we recommend drill-seeding as much of the Heron Pond expansion tract as is topographically feasible with a cover crop of sterile sudangrass (Sorghum sudanese) in mid-May 2000 at a rate of 30 pounds of pure live seed per acre in rows 14 inches apart. Sterile sudangrass is very competitive and will compete effectively against the weeds for soil moisture and light, but the sterile form will not produce viable seeds. The cover crop will also control soil erosion and fugitive dust. The sterile sudangrass can be cut to an 8-inch stubble height in August 2000, with the cut grass being removed from the site to improve the effectiveness of subsequent herbicide treatment of field bindweed and diffuse knapweed. Immediately after the sorghum is cut, we recommend spraying the Heron Pond expansion tract again with a mixture of 1 pint of tordon + 1 quart of 2,4-D per acre. Immediately before native plant seeds are planted, the site should be chisel-plowed to break up the soil surface and to facilitate subsequent seeding (Table A5-10). Chisel plowing can be done between December 2000 and March 2001. Seeds should be planted immediately after chisel plowing. The soils found at the Heron Pond expansion site are the product of human activities such as filling. They are very low in organic matter and nutrients such as nitrogen, phosphorus but have relatively high levels of potassium (Fonda Apostolopoulos, pers. comm.). Nonetheless, they support vigorous stands of alien weeds

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most notably summer cypress, cheatgrass and diffuse knapweed where recent vehicular activity has not destroyed the vegetation. Given the abundance of alien weeds, we believe that amending the soil at the site to increase the levels of organic matter and soil nitrogen would be counterproductive. Perennial, native plants are generally more competitive with annual weeds under low-nutrient conditions, like the Heron Pond expansion site. Amending the soil would, we believe, create more weed problems than it would benefit native plant species establishment. Planting Strategy

We recommend using a rangeland drill to plant native plant seeds. This machine places the seeds at the proper depth on the soil and greatly increases the likelihood of successful stand establishment, plus it reduces the amount of seed needed compared to broadcast seeding. The seeds of many native forb species are expensive and available in small amounts, if at all, commercially. Use a rangeland drill that has the seed tubes behind the wheels and use a slow speed while seeding (< 3 miles her hour). The two mixtures of native grass seeds, for the areas to be subsequently disturbed by detention pond construction or not, can be drill seeded between December 2000 and March 2001 in rows 14 inches apart.

We recommend planting shrubs in clumps of three individuals of different species within 25 feet of planted cottonwood trees to mimic the dispersion patterns found in nature. This will increase the likelihood that at least one of the shrubs in the clump will survive because different shrub species have somewhat different environmental preferences.

We also recommend watering the seeded areas during the first growing season to

reduce the risk of failure of stand establishment. The area can be sprinkle-irrigated on a bi-weekly schedule from June 1 – August 15, 2001, with one inch of water applied per watering. Watering on this schedule would result in a total of 6 inches of water being applied on 6 different dates. Significant natural precipitation events would obviate the need to irrigate as frequently. Weed Control During First Two Growing Seasons

It is critical to control weeds during the first two years of restoration, i.e., in 2001

and 2002. Mowing can be very effective at controlling weeds and promoting the desirable seeded species by reducing the competition for light, water and nutrients exerted by the weeds on the seeded species. Mowing twice during the first and once or twice during the second growing season should be sufficient to control the weeds. The first mowing during the first year should occur in early June when the cool-season weeds are about 1 foot tall and growing rapidly. The second mowing should occur in late July or early August (depending on the timing of summer rainfall) when the warm-season weeds are about 1 foot tall and growing rapidly. The rotary cutting bar of the mower needs to be set high (6 inches off the ground) so it cuts the taller, fast-growing weeds and does not cut the smaller, slow-growing native species. Rotary mowers are superior to

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sickle-bar mowers because the latter can leave a thick mulch of cut material that may shade out small seedlings of native plants. Monitoring Monitoring is the collection and analysis of repeated observations that permit one to evaluate changes in condition and progress towards a land management objective (Elzinga et al. 1998). For the proposed restoration, the purpose of monitoring is to determine if the seeded and planted native species become established and if the weed control program is successful in preventing new weed infestations and in suppressing existing infestations. We assume that relatively few resources will be available for monitoring, given competing needs for resources at Heron Pond. Therefore, we have proposed what we believe to be a minimal level of monitoring that can evaluate the success of the native plant community restoration and weed control efforts. The proposed monitoring is designed to efficiently determine if the restoration is increasing the frequencies of native plant species to the target levels and is reducing noxious weeds to low target frequencies (see Appendix 4 for details). For the temporary restoration of the Heron Pond expansion tract, we recommend a sampling objective of estimating the frequency of native plants (or noxious weeds) within 20% of the true frequency with 80% confidence. Pilot sampling will be necessary to estimate the number of frequency quadrats needed to meet the sampling objective. We suspect that the sampling objective can be met using approximately 200 temporary frequency quadrats, each 25 cm x 25 cm, in each of the two temporary native plant communities that will seeded in 2001. Once the permanent restoration has begun (following construction of the new stormwater detention pond), we recommend extending the monitoring to the other native plant community types restored at Heron Pond. To be efficient in the field, we recommend establishing several temporary transects at stratified, random locations in each community type, with the frequency quadrats being 3 meters apart along each transect. Stratification insures that samples will be distributed throughout the temporary restoration area. For example, one could establish 7 transects, each 90 meters long, each with 30 quadrats, in each of the two temporary native plant communities, for a total of 210 quadrats. Quadrats 3 meters apart can be considered independent samples of the vegetation, thereby greatly increasing the statistical power of the monitoring (Elzinga et al. 1998). In each quadrat, one simply checks on a pre-printed data sheet the plant species that are rooted within the quadrat frame. All of the frequency data for the two temporary restoration areas could be collected in one or two days in the field. We recommend collecting frequency data annually in July to provide annual feedback to the restoration process. Analysis of the frequency data involves calculating estimate for means of the population parameter, frequency, along with an estimate for confidence intervals about the means. Elzinga et al. (1998:367) provide several references for calculating the confidence intervals.

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If the management objectives for the temporary restoration are not met (meaning that the frequency of native plants is too low or the frequency of noxious weeds is too high), Denver Parks will review options for increasing the abundance of native plants and reducing the abundance of noxious weeds. At least one action will be implemented to meet the objective(s). In addition, we recommend establishing one permanent photo points at one end of each of the temporary transects established in 2001. The points can be permanently marked with 18-inch long plastic stakes driven into the ground, each marked with an numbered aluminum tag. Photographs can be taken along each transect when the frequency data are collected annually. For the 2-3 acres of created wetlands, the number of species of wetland plants can be determined simply by walking through the wetland in mid-summer of 2001 and recording the species of wetland plants observed. The basal cover of the wetland plants can be estimated in 25 cm x 25 cm quadrats situated 3 m apart along temporary transects that traverse the width of the created wetland. The data for the quadrats along each transect are averaged, with the transect being the sampling unit. Transects will be relatively short because the constructed wetland will be relatively narrow; therefore, each transect will contain only a few quadrats. Data from adjacent transects may be pooled to increase the sub-sample size. We recommend a sampling objective of estimating the mean basal cover of all wetland species combined within 20% of the true basal cover with 80% confidence. Pilot sampling will be needed to estimate the number of transects needed. If this management objective is not met (meaning that the wetland plants do provide at least 50% basal cover), additional wetland plants will be planted. The species used and the number of plants needed will be determined based on the results of the monitoring. References

Anonymous. 1998. Ecoregion-based conservation in the central shortgrass

prairie. Unpublished report on file at The Nature Conservancy of Colorado, boulder, CO. Apostolopoulos, F. 2000. Colorado Department of Public Health and

Environment, Hazardous Materials and Waste Management Division, Denver, CO. Personal communication with Alan Carpenter, February 3, 2000.

Brune, R. 1998. A vegetation survey of the South Platte River at Denver.

Unpublished report on file at Denver Audubon, Denver, CO.

Elzinga, C. L., D. W. Salzer and J. W. Willoughby. 1998. Measuring and monitoring plan populations. BLM Technical Reference 1730-1. Bureau of Land Management, National Business Center, Denver, CO.

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Jacobs, J. S., M. F. Carpinelli, and R. L. Sheley. 1999. Revegetating noxious-weed infested rangeland. In: R. L. Sheley and J. K. Petroff (eds.) Biology and management of noxious rangeland weeds. Oregon State University Press, Corvallis. Pp. 133-144.

Kittel, G., R. Rondeau, and A. McMullen. 1996. A classification of the riparian vegetation of the Lower South Platte River and parts of the Upper Arkansas Basins, Colorado. Unpublished report prepared for the Colorado Department of Natural Resources and the U. S. Environmental Protection Agency.

Velegala, R. P., R. L. Sheley, and J. S. Jacobs. 1997. Influence of density on

intermediate wheatgrass and spotted knapweed interference. Journal of Range Management 50:523-529.

Weber, W. A. 1990. Colorado flora – eastern slope. University of Colorado

Press, Niwot, CO.

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Table A5-1 Target plant associations for restoration, their geomorphologic settings, and suitable environments at the Heron Pond Natural Area. With the exception of the Sand sagebrush/sand bluestem Shrubland, these plant associations were identified by Kittel et al. (1996) and are listed in order from wetter to drier. Refer to Figure A5-1 for proposed locations of these plant associations. Plant names follow Weber (1990). _______________________________________________________________________ Plant Association Geomorphologic Setting Suitable Environment at Heron Pond Natural Area Hardstem – softstem bulrush (Schoenoplectus lacustris ssp. acutus – S. l. ssp. creber) Plant Association

Shallow, standing water and slow-moving streams

Bottom of new stormwater conveyance channel

Plains cottonwood-(Peach leaf willow)/Coyote willow (Populus deltoides ssp. monilifera-(Salix amygdaloides)/Salix exigua Plant Association

Young alluvial surfaces such as point bars, low stream banks, and overflow areas

Sides of stormwater conveyance channel adjacent to low-flow water level

Plains cottonwood-(Peach leaf willow)/Prairie cordgrass (Populus deltoides ssp. monilifera-(Salix amygdaloides)/Spartina pectinata Plant Association

Well-drained but low-lying areas such as swales and low spots within overflow channels on broad floodplains

Bottom of new stormwater detention pond

Plains cottonwood/Switchgrass (Populus deltoides ssp. monilifera/Panicum virgatum) Plant Association

Low floodplain ridges, slightly elevated point bars, and along stream banks

Sides of new stormwater detention pond

Plains cottonwood/Choke cherry (Populus deltoides ssp. monilifera/Padus virginiana ssp. melanocarpa) Plant Association

Upper terraces and elevated stream banks

Level areas within 20 feet of the edge of the upper slope of the new stormwater detention pond

Plains cottonwood/Snowberry (Populus deltoides ssp. monilifera/Symphoricarpos occidentalis) Plant Association

Elevated ridges and flat areas of the floodplain that are well drained and slightly higher than most of the other surfaces

Dry uplands away from new stormwater detention pond

Sand sagebrush/sand bluestem Shrubland (Oligosporus filifolius/Andropogon hallii Plant Association

Uplands with deep, sandy soils

Reception area for material excavated from stormwater detention pond

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A5-11

Table A5-2 Recommended plant species for restoration of the bottom of the new stormwater detention pond and the stormwater conveyance channel at Heron Pond Natural Area Suitable plant species for restoration are listed in each plant life form category. An asterisk (*) denotes a dominant species. PLS means Pure Live Seeds. _____________________________________________________________________ Characteristics of the physical environment: Slowly flowing water in channel ~ 0.5 foot deep under base flow conditions; more rapidly flowing water during storms; bottom of channel will consist mostly of fine soil and sediment; design grade of channel < 1 percent. Target plant association: Hardstem–softstem bulrush (Schoenoplectus lacustris ssp. acutus – S. l. ssp. creber = Scirpus acutus-Scirpus validus) Plant Association Trees (None) Shrubs (None) Herbaceous plants (average planting density of 1 plant /ft2 with 40% hardstem bulrush; 40% softstem bulrush and balance selected from at least five species listed below; plus sloughgrass seeded at the indicated rate)

Hardstem bulrush (Schoenoplectus lacustris ssp. acutus = Scirpus acutus) *; Super cells Softstem bulrush (Schoenoplectus lacustris ssp. creber = Scirpus validus = Scirpus tabernaemontani)*; Super cells Arrowhead (Sagittaria latifolia); tubers Beaked sedge (Carex utriculata); Super cells Water-plantain (Alisma plantago-aquatica); tubers Water smartweed (Persicaria amphibia); Super cells American germander (Teucrium canadense); Super cells Mannagrass (Glyceria striata); Super cells Sloughgrass (Beckmannia syzigachne); seeded at 5 PLS/ ft2)

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A5-12

Table A5-3 Recommended plant species for restoration of sides of the new stormwater conveyance channel at Heron Pond Natural Area. Suitable plant species for restoration are listed in decreasing order of importance with each plant life form category. An asterisk (*) denotes a dominant species. ____________________________________________________________________ Characteristics of the physical environment: Soil continuously damp from water in the channel moving upward by capillary action; ground water typically 0.5 to 2.0 feet below grade. Target plant association: Plains cottonwood-(Peach leaf willow)/Coyote willow (Populus deltoides ssp. monilifera-(Salix amygdaloides)/Salix exigua. Trees (balled and burlapped 10 foot-tall stock for cottonwood, 5-foot for willow)

Plains cottonwood (Populus deltoides ssp. monilifera) *; 7 trees / acre Peach-leaf willow (Salix amygdaloides) *; 7 trees / acre

Shrubs (1-gallon container-grown stock)

Coyote willow (Salix exigua) *; plant 10% of area of channel sides in patches of 1 plant / ft2 Indigobush (Amorpha fruiticosa); 10 plants / acre in a random pattern

Herbaceous plants (average planting density of 1 plant / ft2; 25% wooly sedge, balance comprised of at least 5 other species including at least 2 forbs)

Wooly sedge (Carex lanuginosa) *; Super cells Nebraska sedge (Carex nebrascensis); Super cells Baltic rush (Juncus arcticus ssp. ater); Super cells Three-square (Schoenoplectus pungens = Scirpus pungens = Scirpus americanus); Super cells Prairie cordgrass (Spartina pectinata); Super cells Foxtail (Alopecurus aequalis); Super cells Sunflower (Helianthus nuttallii); Super cells Swamp milkweed (Asclepias incarnata); Super cells Western fragrant goldenrod (Euthamia occidentalis = Solidago occidentalis); Super cells Joe Pye weed (Eupatorium maculatum); Super cells Sedge (Carex stipata); Super cells Western wheatgrass (Pascopyrum smithii = Agropyron smithii); Super cells

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A5-13

Table A5-4 Recommended plant species for restoration of the bottom of the new stormwater detention pond at Heron Pond Natural Area. Suitable plant species for restoration, listed in plant growth form category. An asterisk (*) denotes a dominant plant species. PLS means Pure Live Seeds. _____________________________________________________________________ Characteristics of the physical environment: Inundated periodically with up to 3 feet of stormwater for up to 7 consecutive days; potential for mild anoxic conditions on pond bottom; slow accumulation of fine sediment on pond bottom; soil on pond bottom relatively permeable to water, at least initially; ground water within 3 feet of bottom of pond at all times. Target plant association: Plains cottonwood-(Peach leaf willow)/Prairie cordgrass (Populus deltoides ssp. monilifera-(Salix amygdaloides)/Spartina pectinata Trees (balled and burlapped;10-foot tall stock for cottonwood, 5-foot for willow)

Plains cottonwood (Populus deltoides ssp. monilifera) *; 5 trees / acre Peach-leaf willow (Salix amygdaloides) *; 7 trees / acre

Shrubs (1-gallon container-grown stock)

Coyote willow (Salix exigua) *; plant 10% of pond bottom in patches of 1 plant / ft2) Yellow willow (Salix lucida ssp. lasiandra); plant 10% of pond bottom in 5-plant patches of 1 plant / 10 ft2

Herbaceous plants (average planting density of 1 plant / ft2; 50% prairie cordgrass, 25% wooly sedge, balance comprised of at least 3 other species including at least 1 forb)

Prairie cordgrass (Spartina pectinata) *; Super cells Wooly sedge (Carex lanuginosa) *; Super cells Streambank wheatgrass (Elymus lanceolatus ssp. riparium) *; Super cells Spikerush (Eleocharis palustris); *; Super cells Baltic rush (Juncus arcticus ssp. ater); Super cells Swamp milkweed (Asclepias incarnata); Super cells Wild licorice (Glycyrrhiza lepidota); Super cells Indian hemp (Apocynum cannabinum); Super cells Prairie gentian (Eustoma grandiflora); broadcast seeded at 10 PLS/ft2 = 1.6 lb/ac

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A5-14

Table A5-5. Recommended plant species for restoration of the sides of the new stormwater detention pond at the Heron Pond Natural Area. Suitable plant species for restoration are listed in each plant growth form category. An asterisk (*) denotes a dominant species. PLS means pure live seed. ______________________________________________________________________ Characteristics of the physical environment: Inundated periodically with 1 - 3 feet of stormwater for up to 7 consecutive days; potential for mild anoxic conditions on deeper portions of pond slopes; soil on sides of pond permeable to water. Target plant association: Plains cottonwood/Switchgrass (Populus deltoides ssp. monilifera/Panicum virgatum) Trees (balled and burlapped;10-foot tall stock for cottonwood, 5-foot for willow)

Plains cottonwood (Populus deltoides ssp. monilifera) *; 7 trees / acre Peach-leaf willow (Salix amygdaloides) *; 7 trees / acre

Shrubs (1-gallon container-grown stock; plant in random pattern with 1 indigo bush and 1 grape plant / 200 ft2; 1 hackberry plant / 1000 ft2)

Indigobush (Amorpha fruiticosa) * Grape (Vitus riparia) * Hackberry (Celtis laevigata ssp. reticulata)

Herbaceous plants (average planting density of 1 plant / ft2; 50% prairie cordgrass, balance comprised of at least 5 other species including at least 1 forb)

Switchgrass (Panicum virgatum) *; Super cells Prairie cordgrass (Spartina pectinata); Super cells Wooly sedge (Carex lanuginosa); Super cells Streambank wheatgrass (Elymus lanceolatus ssp. riparium); Super cells Nebraska sedge (Carex nebrascensis); Super cells Clustered field sedge (Carex praegracilis); Super cells Canada wildrye (Elymus canadensis); broadcast seeded and raked at 18 PLS/ ft2 = 7 lb/ac Alkali sacaton (Sporobolus airoides); Super cells Sedge (Carex athrostachya); Super cells Wild licorice (Glycyrrhia lepidota); Super cells

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A5-15

Table A5-6. Recommended plant species for restoration of the level areas within 20 feet of the edge of the upper slope of the new stormwater detention pond at the Heron Pond Natural Area. Suitable plant species for restoration are listed in each plant growth form category. An asterisk (*) denotes a dominant species. ____________________________________________________________________ Characteristics of the physical environment: Depth to ground water < 3 feet; many plant species can extract water from the water table; soils are well drained; no anoxia in soils. Target plant association: Plains cottonwood/Choke cherry (Populus deltoides ssp. monilifera/Padus virginiana ssp. melanocarpa) Trees (balled and burlapped;10-foot tall stock for cottonwood)

Plains cottonwood (Populus deltoides ssp. monilifera) *; 5 trees / acre) Shrubs (1-gallon container-grown stock; plant 10% of area in chokecherry clumps with 1 plant / 10 ft2; plant another 10% of area with patches using at least 4 different shrub species with average density of 1 plant / 10ft2)

Chokecherry (Padus virginiana ssp. melanocarpa = Prunus v. ssp. m.) * Snowberry (Symphoricarpos occidentalis) Virginia creeper (Parthenocissus inserta) Wild plum (Prunus americana) Skunkbrush (Rhus trilobata) Hackberry (Celtis laevigata ssp. reticulata) Golden currant (Ribes aureum) Wax currant (Ribes cereum) Rose (Rosa woodsii)

Herbaceous plants (all herbaceous plants drill seeded prior to planting shrubs and trees, total overall seed density of 100 PLS/ft2; seed all of the dominant species and at least 4 other species including at least 1 forb)

Switchgrass (Panicum virgatum) *; seeded at 27 PLS/ft2 = 3 lb/ac Prairie sandreed (Calamovilfa longifolia) *; seeded at 26 PLS/ft2 = 3 lb/ac Canada wildrye (Elymus canadensis); seeded at 18 live seeds / ft2 = 7 lb/ac Sand dropseed (Sporobolus cryptandrus); seeded at 24 PLS/ft2 = 0.2 lb/ac Western wheatgrass (Pascopyrum smithii = Agropyron s.); seeded at 8 PLS /ft2 = 3 lb/ac Wooly sedge (Carex lanuginosa); Super cells Bedstraw (Galium triflorum); Super cells Wild licorice (Glycyrrhia lepidota); Super cells

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A5-16

Table A5-7. Recommended plant species for restoration of the dry uplands away from the new stormwater detention pond at the Heron Pond Natural Area that are not reception areas for material excavated from the detention pond. Seeding rates for the grass species will be reduced in proportion to the success of the temporary restoration efforts. Table A5-9 has recommended seeding rates for temporary restoration until the stormwater detention pond is built. Suitable plant species for restoration are listed in each plant growth form category. An asterisk (*) denotes a dominant species. _______________________________________________________________________ Characteristics of the physical environment: Depth to ground water 3 - 8 feet; some plant species can exploit water from saturated zone; soils are well drained; the soil surface is dry nearly all of the time. Target plant association: Plains cottonwood/Snowberry (Populus deltoides ssp. monilifera/Symphoricarpos occidentalis) Trees (balled and burlapped;10-foot tall stock for cottonwood)

Plains cottonwood (Populus deltoides ssp. monilifera) *; 5 trees / acre) Shrubs (1-gallon container-grown stock; plant 10% of area in snowberry clumps with 1 plant / 10 ft2; plant another 10% of area with patches using at least 4 different shrub species with average density of 1 plant / 10ft2)

Snowberry (Symphoricarpos occidentalis) * Virginia creeper (Parthenocissus inserta) Rose (Rosa woodsii) Skunkbrush (Rhus trilobata ssp. aromatica) Wax currant (Ribes cereum) Rubber rabbitbrush (Chrysothamnus nauseosus ssp. graveolens)

Herbaceous plants (all plants drill seeded prior to planting shrubs and trees; maximum total overall seed density of 100 pure live seeds (PLS)/ ft2; seed all of the dominant species and any 10 of remaining species including at least 5 forb species)

Indian ricegrass (Oryzopsis hymenoides) *; 6 PLS/ft2, 1.5 lb/ ac Needle-and-thread (Stipa comata) *; 4 PLS/ft2, 1.5 lb/ ac Prairie sandreed (Calamovilfa longifolia) *; 5 PLS/ft2, 0.6 lb/ ac Sand bluestem (Andropogon hallii) *; 5 PLS/ft2, 1.6 lb/ ac Sand dropseed (Sporobolus cryptandrus) *; 24 PLS/ft2, 0.2 lb/ ac Canada wildrye (Elymus canadensis), 5 PLS/ft2, 1.9 lb/ ac Bottlebrush squirreltail (Elymus elymoides); 8 PLS/ft2, 1.8 lb/ ac Indian grass (Sorghastrum nutans), 3 PLS/ft2, 1.0 lb/ ac Prairie junegrass (Koeleria cristata; 16 PLS/ft2; 0.3 lb/ ac Sideoats grama (Bouteloua curtipendula), 3 PLS/ft2; 0.7 lb/ ac

A5-17

Table A5-7 (cont’d)

Sandberg bluegrass (Poa secunda = Poa sandbergii); 5 PLS/ft2, 0.25 lb/ ac Thickspike wheatgrass (Elymus lanceolatus ssp. dasystachyum); 5 PLS/ft2, 1.4 lb/ ac Switchgrass (Panicum virgatum); 9 PLS/ft2; 1 lb/ac Blue grama (Bouteloua gracilis); 9 PLS/ ft2; 0.5 lb/ac Sedge (Carex brevior); 1 PLS/ ft2; 0.1 lb/ac Beardtongue (Penstemon albidus); 1 PLS/ ft2; 0.1 lb/ac Blanket flower (Gaillardia aristata); 1 PLS/ ft2; 0.3 lb/ac Locoweed (Oxytropus sericea and O. lambertii); 1 PLS/ ft2; 0.2 lb/ac for each Prairie coneflower (Ratibida columnifera); 3 PLS/ ft2; 0.1 lb/ac Prairie gayfeather (Liatris punctata); 1.5 PLS/ ft2; 0.5 lb/ac Purple prairie clover (Dalea purpurea); 1 PLS/ ft2; 0.2 lb/ac White prairie clover (Dalea candida); 0.8 PLS/ ft2; 0.1 lb/ac Spiderwort (Tradescantia occidentalis); 1 PLS/ ft2; 0.1 lb/ac Ragwort (Senecio spartioides); 1 PLS/ ft2; 0.5 lb/ac

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A5-18

Table A5-8. Recommended plant species for restoration of the dry uplands away from the new stormwater detention pond at the Heron Pond Natural Area that will be reception areas for material excavated from the detention pond. Table A5-9 for recommended seeding for temporary restoration of this area. Suitable plant species for restoration are listed in each plant growth form category. An asterisk (*) denotes a dominant species. PLS means Pure Live Seeds. _______________________________________________________________________ Characteristics of the physical environment: Depth to ground water >10 feet; none of the plant species can exploit water from saturated zone; soils are well drained; the soil surface is dry nearly all of the time. Target plant association: Sand sagebrush/sand bluestem Shrubland (Oligosporus filifolius/Andropogon hallii) Trees (none) Shrubs (1-gallon container-grown stock; plant in random pattern with overall average density of 1 plant / 100ft2)

Sand sage (Oligosporus filifolius = Artemisia filifolia) Herbaceous plants (all plants drill seeded prior to planting shrubs and trees; total overall grass seed density of 100 PLS/ ft2; seed all of the dominant species and any 10 of remaining species including at least 5 forb species)

Prairie sandreed (Calamovilfa longifolia) *; 5 PLS/ft2, 0.6 lb/ ac Needle-and-thread (Stipa comata) *; 4 PLS/ft2, 1.5 lb/ ac Sand bluestem (Andropogon hallii) *; 5 PLS/ft2, 1.6 lb/ ac Sand dropseed (Sporobolus cryptandrus) *; 24 PLS/ft2, 0.2 lb/ ac Indian ricegrass (Oryzopsis hymenoides) *; 6 PLS/ft2, 1.5 lb/ ac Bottlebrush squirreltail (Elymus elymoides); 8 PLS/ft2, 1.8 lb/ ac Prairie junegrass (Koeleria cristata; 16 PLS/ft2; 0.3 lb/ ac Sideoats grama (Bouteloua curtipendula), 3 PLS/ft2; 0.7 lb/ ac Thickspike wheatgrass (Elymus lanceolatus ssp. dasystachyum); 5 PLS/ft2, 1.4 lb/ ac Blue grama (Bouteloua gracilis); 9 PLS/ ft2; 0.5 lb/ac Beardtongue (Penstemon albidus); 1 PLS/ ft2; 0.1 lb/ac Blanket flower (Gaillardia aristata); 1 PLS/ ft2; 0.3 lb/ac Prairie coneflower (Ratibida columnifera); 3 PLS/ ft2; 0.1 lb/ac Purple prairie clover (Dalea purpurea); 1 PLS/ ft2; 0.2 lb/ac White prairie clover (Dalea candida); 0.8 PLS/ ft2; 0.1 lb/ac Spiderwort (Tradescantia occidentalis); 1 PLS/ ft2; 0.1 lb/ac

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A5-19

Table A5-9. Recommended plant species and seeding rates for temporary restoration of two portions of the Heron Pond expansion tract to help control noxious weeds List A is for the part of the Heron Pond expansion tract that will be drastically disturbed when the stormwater detention pond in constructed while list B is for the part of the tract that will not be disturbed. PLS means pure live seeds. All species are drill seeded, with a target overall seed density of between 100-120 PLS / ft2. _______________________________________________________________________ List A Canada wildrye (Elymus canadensis), 20 PLS/ft2, 7.6 lb/ ac Sand dropseed (Sporobolus cryptandrus), 100 PLS/ft2, 0.8 lb/ ac List B Canada wildrye (Elymus canadensis), 5 PLS/ft2, 1.9 lb/ ac Bottlebrush squirreltail (Elymus elymoides), 8 PLS/ft2, 1.8 lb/ ac Indian grass (Sorghastrum nutans), 3 PLS/ft2, 1.0 lb/ ac Indian ricegrass (Oryzopsis hymenoides), 12 PLS/ft2, 3.0 lb/ ac Needle-and-thread (Stipa comata); 8 PLS/ft2, 3.0 lb/ ac Prairie junegrass (Koeleria cristata; 16 PLS/ft2, 0.3 lb/ ac Prairie sandreed (Calamovilfa longifolia), 10 PLS/ft2, 1.2 lb/ ac Sideoats grama (Bouteloua curtipendula), 3 PLS/ft2, 0.7 lb/ ac Sand bluestem (Andropogon hallii), 10 PLS/ft2, 3.2 lb/ ac Sand dropseed (Sporobolus cryptandrus), 24 PLS/ft2, 0.2 lb/ ac Thickspike wheatgrass (Elymus lanceolatus ssp. dasystachyum), 5 PLS/ft2, 1.4 lb/ ac ______________________________________________________________________

A5-20

A5-21

Table A5-10. Two alternative sequences of steps for interim restoration of the Heron Pond expansion tract at Heron Pond Natural Area from 2000-2002 The left-hand sequence uses herbicides for weed control, while the right-hand sequence does not. We recommend the strategy that uses herbicides because we believe they offer superior short-term control of field bindweed and diffuse knapweed. Uses Herbicides Does Not Use Herbicides First Week of May 2000 Spray infested portions of tract with tordon + 2,4-D to kill field bindweed and diffuse knapweed

First Two Weeks of May 2000 Graze entire tract with goats for two weeks; introduce biological control insects for diffuse knapweed

Third Week of May 2000 Drill seed cover crop of sterile sorghum

Third Week of May 2000 Drill seed cover crop of sterile sorghum

Middle of August 2000 Harvest and remove sterile sorghum, leaving stubble height of 8 inches

Middle of August 2000 Leave sterile sorghum in place and graze entire tract with goats for one month

Middle of August 2000 Immediately after harvesting sorghum, spray infested portions of tract with tordon and 2,4-D to control field bindweed and diffuse knapweed

Middle of August 2000 See box above

December 2000 – March 2001 Chisel-plow site to control weeds and loosed compacted soil

December 2000 – March 2001 Chisel-plow site to control weeds and loosed compacted soil

December 2000 – March 2001 Immediately after chisel plowing, drill seed native grasses

December 2000 – March 2001 Immediately after chisel plowing, drill seed native grasses

June 2001 Mow tract to control cool-season weeds

June 2001 Mow tract to control cool-season weeds

June – August 2001 Sprinkle irrigate entire tract with 1 inch of water bi-weekly starting June 1

June – August 2001 Sprinkle irrigate entire tract with 1 inch of water bi-weekly starting June 1

August 2001 Mow tract to control warm-season weeds

August 2001 Mow tract to control warm-season weeds

June 2002 In needed, mow tract to control cool-season weeds

June 2002 In needed, mow tract to control cool-season weeds

August 2002 In needed, mow tract to control warm-season weeds

August 2002 In needed, mow tract to control warm-season weeds