SP 03-09

Invasive Weed Identificationfor Nevada

Wayne S Johnson, Associate Professor, Applied Economics and Statistics, College ofAgriculture, Biotechnology and Natural Resources; IPM Specialist, University of Nevada

Cooperative ExtensionRobert Wilson, Extension Educator, University of Nevada Cooperative ExtensionJessica Graham, Undergraduate Research Assistant, University of Nevada, Reno

Invasive weeds are draining Nevada’s

economic and natural resources

How to use this handbook toidentify invasive plants in Nevada

1. Carry the handbook with you whenever you are outand about in Nevada. Put it in your glove compartment,pack, lunch box, or pocket.

2. Refer to it when you encounter a plant that yoususpect may be an invasive plant.

3. Use the pictures and description to identify theinvasive plant.

4. Fill out the survey form in the back of the bookeach time you identify an invasive plant in a new location.Feel free to photocopy additional forms.

5. If you have access to a Global Positioning System(GPS) unit, please note the positional coordinates.

6. On the reverse side of the survey form, draw asimple map to describe the site where the invasiveplant is encountered. Put as much detail in thedrawing as you like. Ask yourself when you finish, “Isthe map drawn well enough that someone unfamiliarwith the area could find the site and these plants?”

7. Send the completed form and map to: Dr. WayneS Johnson, Department of Applied Economics andStatistics, Mail Stop 204, University of Nevada,Reno, NV, 89557-0105.

Additional Web Resources:

Nevada Department of Agriculture’s Nevada WeedAction Committeehttp://agri.nevada.gov/nwac/index.htm

University of Nevada Cooperative Extensionhttp://www.unce.unr.edu/pubs.html

Natural Resources Conservation Servicehttp://www.nv.nrcs.usda.gov/plants.html

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Introduction

Invasive plants are displacing diverse plantcommunities and greatly impacting Nevada’s naturaland economic resources. Private and public landmanagers struggle to protect their lands frombecoming unproductive, wildlife unfriendly monocul-tures of costly alien weeds. To become a problem, invasive, competitiveplants must be introduced into an area, they mustestablish and reproduce, and finally, they mustdisperse. Control or management is easiest andleast expensive during the first two stages anddifficult to impossible, and very expensive, during thelast. Thus, the key to control is to identify potentialweed infestations at very early stages and theneradicate them or prevent their spread. This publication provides a tool to aid in theidentification of invasive weeds that may be found inNevada. Some of these weeds are not present inNevada; however, their potential for invasion andestablishment warrants concern. All of these weedshave invaded one or more of Nevada’s neighboringstates. New weeds in an area should always beidentified and appropriate management initiated. Inmany cases, eradication may be possible, while somesituations will warrant containment only. Contact alocal plant professional in your county for advice andhelp. All of the invasive plants in this booklet are listed asnoxious weeds in the Nevada Revised Statutes, but notall noxious weeds are invasive. Therefore, not all of thenoxious weeds in Nevada are included in this handbook.The distribution of these noxious plants in commerce isprohibited and their control or management is mandated. Weed control recommendations frequently change.For current control practices, contact your county Univer-sity of Nevada Cooperative Extension Educator or weedsupervisor.

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4

Index of invasive plants by scientificfamily name:

Botanical NameAcroptilon repensAlhagi pseudalhagiCardaria drabaCarduus nutans

Centaurea calcitrapaCentaurea diffusaCentaurea ibericaCentaurea maculosaCentaurea melitensis

Centaurea solstitialisCentaurea virgata spp. squarrosaChondrilla junceaCirsium arvenseCrupina vulgarisCynoglossum officinaleEuphorbia esulaHydrilla verticillataHypericum perforatum

Isatis tinctoriaLepidium latifolium

Linaria dalmaticaLinaria vulgarisLythrum salicariaMyriophyllum spicatumOnopordum acanthiumPeganum harmalaPennisetum setaceumPotentilla rectaRorippa austriacaSalvia aethiopisSalvinia molestaTaeniatherum caput-medusaeTamarix ramosissimaZygophyllum fabago

PagesCommon NameRussian knapweedCamelthornHoary cress/WhitetopMusk thistle/ Nodding thistlePurple starthistleDiffuse knapweedIberian starthistleSpotted knapweedMalta starthistle/ TocaloteYellow starthistleSquarrose knapweed

Rush skeletonweedCanada thistleCommon crupinaHoundstongueLeafy spurgeHydrillaSt. Johnswort/ Klamath weedDyer’s woadPerennial pepperweed/ Tall whitetopDalmatian toadflaxYellow toadflaxPurple loosestrifeEurasian watermilfoilScotch thistleAfrican RueGreen fountain grassSulfur cinquefoilAustrian fieldcressMediterranean sageGiant salviniaMedusahead

Saltcedar/TamariskSyrian beancaper

18-1946-4734-358-9

10-1112-1310-1114-1516-17

20-2122-23

24-2526-2728-2932-3344-4550-5142-43

36-3738-39

64-6566-6754-5548-4930-3170-7156-5760-6140-4152-5362-6358-59

68-6972-73

5

Index of invasive plants by commonname:

Common NameAfrican RueAustrian fieldcressCamelthornCanada thistleCommon crupinaDalmatian toadflaxDiffuse knapweedDyer’s woadEurasian watermilfoilGiant salviniaGreen fountain grassHoary cress/WhitetopHoundstongueHydrillaIberian starthistleLeafy spurgeMalta starthistle/ TocaloteMediterranean sageMedusahead

Musk thistle/ Nodding thistlePerennial pepperweed/ Tall whitetopPurple loosestrifePurple starthistleRush skeletonweedRussian knapweedSaltcedar/TamariskScotch thistleSpotted knapweedSquarrose knapweed

St. Johnswort/ Klamath weedSulfur cinquefoilSyrian beancaperYellow starthistleYellow toadflax

PagesBotanical NamePeganum harmalaRorippa austriacaAlhagi pseudalhagiCirsium arvenseCrupina vulgarisLinaria dalmaticaCentaurea diffusaIsatis tinctoriaMyriophyllum spicatumSalvinia molestaPennisetum setaceumCardaria drabaCynoglossum officinaleHydrilla verticillataCentaurea ibericaEuphorbia esulaCentaurea melitensis

Salvia aethiopisTaeniatherum caput-medusaeCarduus nutans

Lepidium latifolium

Lythrum salicariaCentaurea calcitrapaChondrilla junceaAcroptilon repensTamarix ramosissimaOnopordum acanthiumCentaurea maculosaCentaurea virgata spp. squarrosaHypericum perforatum

Potentilla rectaZygophyllum fabagoCentaurea solstitialisLinaria vulgaris

70-7140-4146-4726-2728-2964-6512-1336-3748-4962-6356-5734-3532-3350-5110-1144-4516-17

52-5358-59

8-9

38-39

54-5510-1124-2518-1968-6930-3114-1522-23

42-43

60-6172-7320-2166-67

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Index of invasive plants by flower color:(Several invasive species may exhibit more than oneflower color, or the flower may fade to white.)

Common Name PagesBotanical Name

WhiteAfrican rueDiffuse knapweedHoary cress/WhitetopMediterranean sagePerennial pepperweed/ Tall whitetopSyrian beancaper

YellowAustrian fieldcressDalmatian toadflaxDyer’s woadLeafy spurgeMalta starthistle/ TocaloteRush skeletonweedSt. Johnswort/ Klamath weedSulfur cinquefoilYellow starthistleYellow toadflax

Pink to purpleCommon crupinaMusk thistle/Nodding thistleRussian knapweedSaltcedar/TamariskSpotted knapweedSquarrose knapweed

PurpleCanada thistleHoundstongueIberian starthistlePurple loosestrifePurple starthistleScotch thistle

Peganum harmalaCentaurea diffusaCardaria drabaSalvia aethiopisLepidium latifolium

Zygophyllum fabago

Cirsium arvenseCynoglossum officinaleCentaurea melitensisLythrum salicariaCentaurea calcitrapaOnopordum acanthium

Rorippa austriacaLinaria dalmaticaIsatis tinctoriaEuphorbia esulaCentaurea melitensis

Chondrilla junceaHypericum perforatum

Potentilla rectaCentaurea solstitialisLinaria vulgaris

Crupina vulgarisCarduus nutans

Acroptilon repensTamarix ramosissimaCentaurea maculosaCentaurea virgata spp. squarrosa

70-7112-1334-3552-5338-39

72-73

40-4164-6536-3744-4516-17

24-2542-43

60-6120-2166-67

28-298-9

18-1968-6914-1522-23

26-2732-3310-1154-5510-1130-31

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Index of invasive plants by flower color:(Several invasive species may exhibit more than oneflower color, or the flower may fade to white.)

Common Name PagesBotanical Name

Pinkish purple to maroonCamelthorn

Aquatic PlantsWhite to light pinkishEurasian watermilfoil

No FlowersGiant salvinia

White to ReddishHydrilla

Green GrassesGreen fountain grassMedusahead

Myriophyllum spicatum

Pennisetum setaceumTaeniatherum caput-medusae

46-47

48-49

62-63

50-51

56-5758-59

Alhagi pseudalhagi

Salvinia molesta

Hydrilla verticillata

Musk thistle AsteraceaeCarduus nutans L.

Purple flower headwith distinctivebracts (left).

Seedling with palemidrib and yellowspines on lobedmargins (right).

Mature musk thistle plant.

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Carduus nutans L.Asteraceae Musk thistle

Origin: Southern Europe and western Asia

Description: Introduced into the United States early inthe twentieth century, musk thistle or nodding thistle hasspread throughout the United States and Canada. Abiennial or sometimes a winter annual, it stands 30 to 42inches tall, but may grow to 72 inches tall. The darkgreen leaves have a light green central vein, deeply cutlobes, and a spiny edge. Directly attached to the stem,the narrow leaves are up to 8 inches long and alternatelyarranged. Single flower heads grow on the ends of longstalks, are 1 1/2 to 3 inches in diameter, and usually bendover at the neck. The flowers are deep rose, violet orpurple, and occasionally white. They have broad, spine-tipped bracts at their base, the bottom row or 2 of whichare bent under or recurved. Flowering occurs from Juneto September. The fruits are 3/16 inch long, shiny, andyellowish brown with a plume of white hair 3/4 inch long atone end. Musk thistles reproduce by seed.

Habitat Preferences: Musk thistles germinate andgrow under a wide range of environmental condi-tions. They invade pastures, range and forest lands,grain fields, stream and ditch banks, roadsides,waste areas, vacant lots, abandoned farmland, andvery dry sites. It spreads rapidly and forms densestands which crowd out other plants in both moistand dry sites.

Management: Tillage, hoeing, and hand pulling thatsevers the root below the soil surface before seed isproduced is recommended. Mowing alone, especiallya single pass, is not recommended, as seed will beproduced. The introduced musk thistle weevil feedson the seeds and limits the spread of this weed.Chemical control is effective and available. Goodgrazing management stimulates grass growth andkeeps pastures and rangeland healthy and moreresistant to musk thistle invasion.

Purple and Iberian starthistles AsteraceaeCentaurea calcitrapa L. and C. iberica Trev. ex Spreng.

Mature Iberian starthistle plant.

Purple starthistleflower with spine-

tipped bracts.

Iberian starthistle flowerhas a round head and

light purple flower.

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Asteraceae Purple and Iberian starthistles

Origin: Europe

Description: Purple starthistle grows 12 to 48inches tall with a stout taproot, and a branchedstem. Its stems and leaves are covered with cobwebbyhairs that are lost or smooth out with maturity. Its lowerleaves are deeply divided into oblong, linear segments,while the upper leaves are narrow and undivided. Tiny,clear globules are lightly pitted on the bottoms of itsleaves. Rosette leaves at the base of the plant aredeeply divided, with a circle of spines in the center of theolder rosettes. The lavender to deep purple flowerclusters have many heads 3/4 to 1 inch long with spine-tipped bracts. Its seeds are about 1/8 inch long, lackbristles, and are straw-colored with dark brown spots.Flowering occurs from July to October.Iberian starthistle is very similar to purplestarthistle, thus mature seed heads are needed todistinguish between them. Iberian seeds have aplume of flattened bristles about half as long as theseed at one end. Its flowers tend to be a lighterpurple with a more round head than purplestarthistle and occur in July and August. Bothstarthistle species reproduce rapidly by seed.

Habitat Preferences: Purple starthistle is moreabundant on fertile sites, while Iberian starthistleestablishes along streambeds or wet areas. Bothweeds infest rangelands, pasture, and roadsides.

Management: Grubbing or digging may providecontrol of minor infestations and is most effective ifdone when the plant is a young rosette. Cutting theplant below the soil surface early in the growingseason may be effective. Mowing is ineffective andmay make the problem worse by spreading seeds ormaking the plant produce more flowers and seed heads.There are currently no biological controls for either ofthese starthistles. Herbicide application will be moresuccessful if done in the spring.

Centaurea calcitrapa L. and C. iberica Trev. ex Spreng.

Diffuse knapweed AsteraceaeCentaurea diffusa Lam.

Flower bracts areyellow-spined withfine teeth along thespine’s margin (right).

Seedling with finelydivided leavescovered with shorthairs (left).

Mature diffuse knapweed plant.

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Centaurea diffusa Lam.Asteraceae Diffuse knapweed

Origin: Eurasia

Description: Diffuse knapweed is a finely-branchedannual or short-lived perennial that grows 12 to 24inches tall. The stiff stems are rough to the touch.Its leaves are covered with fine hairs and are finelydivided except for the smaller entire leaves of theinflorescence. The plant produces narrow flowerheads with white to rose or purplish flowers from Julyto frost. The margins of the bracts on the base ofthe flowers (involucre) are divided like the teeth of acomb. Each bract is tipped with a yellow, slenderspine. The seed heads are persistent over winter. Theseeds (achenes) are brown or grayish and lack a tuft ofhairs (pappus).

Habitat Preferences: Diffuse knapweed infests road-sides, waste areas, dry rangelands, and disturbed sites.This highly competitive plant may dominate rangelandsin Nevada that receive less than 15 inches of annualprecipitation. It threatens to exclude many desirablespecies from pastures and rangelands. Fortunately, it isless competitive on shallow or very coarse-textured soils.

Management: The seed is commonly spread byequipment, vehicles, and the sale and movement ofcontaminated sand, gravel, and soil. Sanitation is thebest line of defense. Pulling or digging small infesta-tions of diffuse knapweed is effective but must berepeated until the seed bank is depleted, which takesseveral years. Mowing is not recommended as it maystimulate new knapweed growth and reduce competitionfrom other plants. Cultivation controls this weed andgrazing may be effective if done in the rosette through thebud stage. Burning may be used to remove plant debrisand improve herbicide efficacy, but diffuse knapweedresprouts following fire if sufficient moisture isavailable. Several herbicides control it on rangeland,and there are 12 insects established in the westernUnited States that attack diffuse knapweed. In theright environment, all these are effective in slightlyreducing competitiveness.

Spotted knapweed AsteraceaeCentaurea maculosa Lam.

Pinkish purpleflowers havefringed bractstipped with darkspots (right).

Spring rosettes havedeeply lobed leaves (left).

Mature spotted knapweed plant.

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Centaurea maculosa Lam.Asteraceae Spotted knapweed

Origin: Eurasia

Description: Spotted knapweed is a biennial orshort-lived perennial with a stout taproot. It hasone or more branched stems and grows 12 to 36inches tall. The leaves grow alternately along thestem. Basal leaves grow up to 6 inches long, arenarrowly elliptic to oblanceolate, and are entire topinnately parted. The leaves higher up the stem arepinnately divided. Single flowers develop at theend of branches with stiff bracts at their base thatare tipped with a dark comblike fringe. The ray flowersare pinkish purple, or rarely cream-colored, and areproduced from June to frost. The seeds are 1/8 inch longand are tipped with a tuft of persistent bristles.

Habitat Preferences: Spotted knapweed hasdisplaced diverse plant communities in Montana,Utah, and Wyoming. A threat to rangelands, knap-weeds invade disturbed soil. Their early springgrowth makes them competitive for soil moistureand nutrients. In Nevada, this plant may dominaterangelands that receive less than 10 inches ofannual precipitation. There is evidence that knap-weeds release chemical substances that inhibitgermination and growth of surrounding vegetation.

Management: The seed is dispersed by vehicles, bysale of dried specimens for floral arrangements, andby movement of contaminated sand, gravel, andsoil. As a first line of defense, prevent its move-ment. A variety of insects have been released onspotted knapweed to reduce seed production,including insects that damage the roots, shoots,leaves, and flowers. Burning and fertilization areineffective. Cultivation, grazing, or mowing mayhave some positive effects. Careful hand pulling ofsmall infestations can provide effective control ifentire plants are removed before they produceseeds. Herbicides are available to control spottedknapweed, but regular reapplications are necessaryuntil the seed in the soil have all germinated.

Malta starthistle AsteraceaeCentaurea melitensis L.

Malta starthistle plant.

Malta starthistlestems are winged.

The dandelion-likeyellow flower has many

spiny bracts at its base.

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Centaurea melitensis L.Asteraceae Malta starthistle

Origin: Southern Europe

Description: Malta starthistle, or tocalote, is anannual or biennial. Erect stems are branched, hairy,rough, and winged. Basal leaves are lobed with ashort stalk. Stem leaves are narrowly lanceolate,entire or sparsely toothed, and without a stalk(sessile). Ovoid flower heads are solitary on 2 to 3clusters at the tips of the branches. On the flowerbases, the bracts (phyllaries) are straw-colored andtinged with purple or brown, with sparse wooly hairs,ending in a flattened spine. Flowers are yellow andoccur from April to September. Seeds are lightbrown with longitudinal lines, a pappus of unequalbristles, and a slightly hooked base. Both malta andyellow starthistles have yellow flowers and wingedstems, but can be distinguished between as maltastarthistle has shorter (less than 2/5 inch) phyllaryspines with a tiny pair of lateral spines aboutmidlength along a few of the spines.

Habitat Preferences: Malta starthistle is found on opendisturbed sites, grasslands, rangeland, open wood-lands, fields, pastures, roadsides, waste places, andcultivated fields.

Management: Small infestations may be hand pulledover several years. Regular cultivation for several yearsis effective. Mowing and early season grazingchange the plant to a prostrate form that mayproduce more flowers, so neither are recommended.Several insects may attack the seedhead, but theireffectiveness is limited. Herbicides are available.

AsteraceaeRussian knapweedAcroptilon repens (L.) DC.

The bracts of thepinkish purple flowershave papery tips (right).

The fine hairs coveringthe toothed leaves ofnewly emerging plantsgives them a blue-greencolor (left).

Mature Russian knapweed plant.

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AsteraceaeAcroptilon repens (L.) DC.

Russian knapweed

Origin: Eurasia; the Caucasus region between theBlack and Caspian Seas

Description: Russian knapweed is a perennialweed. Propagated by seeds, this weed also formsdense colonies by adventitious shoots from widelyspreading black roots. Roots may grow more than8 feet deep. Stems are erect and openly branched onplants that grow 18 to 36 inches tall. Blue-green leaveson emerging plants are toothed and covered with finehairs. Alternately arranged on the stem, the lower leavesare deeply lobed and 2 to 4 inches long, while the upperleaves are entire or serrate and narrowing to a stalkless(sessile) base. The flower heads are 1/4 to 1/2 inch indiameter and solitary at the tip of leafy branchlets. Pinkflowers are common, but flower color may range fromwhite to lavender. Many pearly bracts with rounded oracute, papery margins cover the base of the flower(involucre). Flowers occurs from June through frost.Seeds (achenes) are 1/8 to 1/4 inch long and havemany white bristles.

Habitat Preferences: Russian knapweed colonizescultivated fields, orchards, pastures, roadsides, andrangelands. It does not establish readily in mosthealthy, natural environments, but if it becomesestablished in a disturbed area it will encroach into anearby healthy plant community. This plant mayeasily dominate cultivated fields and rangelands inNevada where the water table is 20 feet or lessunder the soil surface.

Management: Cultivation and moving infested soilsand contaminated equipment spreads this weed.Temporary management of Russian knapweed canbe achieved with herbicides applied in late fall, butlong-term reductions must include planting competi-tive plant species. Likewise, the correct applicationof herbicides to control this weed before establishingperennial grasses is important. The biologicalcontrol organisms introduced to control Russianknapweed have not proven effective.

Yellow starthistle AsteraceaeCentaurea solstitialis L.

Mature yellow starthistle plant.

Seedling plantleaves have deeplylobed margins withpointed tips (left).

Yellow flowerswith ¾-inch longspines (right).

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Centaurea solstitialis L.Asteraceae Yellow starthistle

Origin: Europe

Description: Mature plants grow 12 to 36 inchestall. Yellow starthistle seedlings have oblong, tongue-shaped seed leaves (cotyledons). There are 3 types oftrue leaves. Basal leaves are 2 to 3 inches long anddeeply lobed. Lower stem leaves are narrow withblades that extend down the stem forming wings. Theupper leaves are short, 1/2 to 1 inch long, narrow, andsharply pointed. A cottony pubescence gives them awhite to gray-green color. The rigid stems are spread-ing, branched from the base, and covered with white togray, loose, cottony hairs. The 1-inch wide dandelion-like, bright yellow flowers occur singly at the ends of thebranches from May through December. They producelong, sharp, rigid, unbranched, 3/4-inch, straw-coloredspines at their base. The lowest spines are 3-parted.This plant spreads by seeds that are either light-coloredwith bristles or dark to black without bristles.

Habitat Preferences: Yellow starthistle infestscultivated fields, pastures, waste lands, roadsides,and rangelands in the west. Outbreaks are occur-ring in Nevada and may dominate rangelands withannual precipitation of less than 15 inches.

Management: Infested rangeland is avoided bygrazing animals. Horses forced to eat yellowstarthistle may die from “chewing disease.” Cattle andsheep may graze yellow starthistle early; after flowering,only goats will eat it. Hand pulling is effective in smallareas when the entire root is removed. Mowing isexpensive and can result in prostrate plants that con-tinue to flower. Burning is effective in combination withchemical treatments and revegetation with a perennialgrass. Various herbicides are available for control.Release of several insects and a disease have beenmarginally effective and are still being investigated.Timing of control methods is critical to success.

Squarrose knapweed AsteraceaeCentaurea virgata Lam. var. squarrosa (Willd.) Boiss.

Mature squarrose knapweed plant.

Flower head showingrecurved bract tips(left).

Seedling showingdeeply indented gray-green leaves (right).

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Squarrose knapweedAsteraceaeCentaurea virgata Lam. var. squarrosa (Willd.) Boiss.

Origin: Eastern Mediterranean

Description: Squarrose knapweed is a long-livedperennial that grows 12 to 36 inches tall. It grows ataproot. The branched stems have deeply dis-sected, alternate lower leaves and bract-like upperleaves. Flower clusters occur from June to Augustand are small with 4 to 8 rose- or pink-colored flowers,each less than 1/2 inch long. The flowers have an urn-shaped base covered with bracts and usually develop nomore than 3 to 4, 1/8-inch long, dull brown seeds withstraw-colored lines and bristles about half as long as theseed. The bract tips are recurved or spreading and haveterminal spines longer than the lateral spines on eachbract. Squarrose knapweed is often confused withdiffuse knapweed, but it is a true perennial, its bracts arerecurved, its seed heads fall off the stems soon after theseeds mature, and its seed has hairs (pappus), whilediffuse knapweed seed is hairless.

Habitat Preferences: Squarrose knapweed is notcommon, but is found in dry rangelands of California,Oregon, and Utah. Seeds are easily spread bylivestock and wildlife. Once established, squarroseknapweed is difficult to control. It will take vigilanceto keep it from becoming established in Nevada,particularly in drier rangelands.

Management: Small infestations may be eradicatedby grubbing or digging the roots with a shovel. Handpulling is ineffective. Use tillage in pastures andfields. Herbicides are registered for control ofknapweeds on rangeland. Most are effective whensufficient precipitation carries them into the soil.Grazing is not recommended as seeds stick toanimal coats or get lodged in hooves. There are 6insects introduced for biological control. Large range-land infestations should use a combination of herbi-cides, revegetation with perennial forage species, andimproved grazing management. Prescribed fire may beeffective in conjunction with herbicide treatments andrevegetation.

Rush skeletonweed AsteraceaeChondrilla juncea L.

Rosettes have redhairs when stemelongation starts inearly summer (left).

Strap-shaped, yellowpetals have a flatend with distinctlobes (right).

Mature rush skeletonweed plant.

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AsteraceaeChondrilla juncea L.

Rush skeletonweed

Origin: Eurasia

Description: A perennial, rush skeletonweed grows12 to 48 inches tall and has a deep, extensive rootsystem. Its stems have coarse, red hairs that benddownward 4 to 6 inches up their base. The stem ishairless and smooth above. Sharply-toothed leavesform a dandelion-like rosette that withers as theflower stem develops. Leaves up the stem areinconspicuous, narrow, and entire. The green stemsphotosynthesize. The plant exudes a milky latexwhen cut or damaged. The flowers are scatteredon the branches, are approximately 3 /4 inch indiameter, and have 7 to 15 yellow, strap-shapedpetals. Flowers and the pale brown to nearly black, 1/8 -inch long seeds are produced mid-July through frost.The seeds are ribbed with tiny, scaly projections on topand a long beak with soft, white bristles at one end.

Habitat Preferences: It inhabits well-drained, light-textured soils along roadsides and in rangelands,grain fields, and pastures. This plant prospers indisturbed soils and with 9 to 59 inches of annualprecipitation. It is growing in Elko and Douglascounties in Nevada and infests millions of acres inIdaho, Oregon, Washington, Montana, and California.

Management: Hand pulling and grubbing areeffective in small, young infestations, but new plantswill emerge from severed roots and buried seeds.Mowing and cultivation are ineffective; they increasethe infestation. Planting competitive legumes canreduce populations of rush skeletonweed. Early,repeated grazing by sheep can reduce or preventproduction of rosettes and seed. Herbicides areineffective due to a lack of leaf surface; use surfac-tants to improve uptake of the chemical into thestems. Three biological control agents are availablethat reduce its competitiveness with other vegeta-t ion.

Canada thistleCirsium arvense (L.) Scop.

Asteraceae

Clusters of purpleflower heads havespineless bracts (left).

Rosettes with spiny-tipped, wavy leavesappear in early spring(right).

Mature Canada thistle plant.

27

Canada thistleAsteraceaeCirsium arvense (L.) Scop.

Origin: Southeastern Eurasia

Description: Canada thistle is a colony-formingperennial with deep and extensive horizontal roots.Its stems are 12 to 48 inches tall, ridged, andbranched above. Its alternate, oblong or lance-shaped leaves lack petioles, are sessile, and aredivided into spiny-tipped, irregular lobes. Pink orpurple flowers are borne in heads 1/2 to 3/4 inch indiameter and can be male or female borne onseparate plants (dioecious). The involucral bracts atthe base of the flower are spineless. Canada thistlefruits are about 1/8 inch long, somewhat flattened,and brownish, with a tuft of hair at the top. Itreproduces through seed dispersal as well as byvegetative spread from horizontal creeping roots.Flowering occurs in July and August.

Habitat Preferences: Canada thistle has a widehabitat range and is fairly adaptable. It is usuallyfound in open areas with moderate or medium soilmoisture, and favors clay soils. It is mostly found alongroadsides and railroad rights-of-way, and on rangeland,forest land, lawns, gardens, cropland, and abandonedfields. Canada thistle grows best in places with annualprecipitation of 16 to 30 inches.

Management: Hand pulling and burning are ineffec-tive due to Canada thistle’s extensive root system.Both cause rapid resprouting from the roots. Fre-quent cultivation can be effective if all shoots areeliminated every time. Mowing repeatedly iseffective in alfalfa and other forage crops. Its spinyleaves make Canada thistle inedible. There areseveral biological control agents registered for thisplant. Single herbicide applications will not providelong-term control. Applying herbicides at the properrate and time is important and, as with mostinvasive weeds, requires follow-up management forseveral years.

Common crupina AsteraceaeCrupina vulgaris Cass.

Mature common crupina plant.

Mature flowerheads with purpleflowers (right).

Seedling showingthe fleshy, oblongcotyledons (left).

29

Common crupinaAsteraceaeCrupina vulgaris Cass.

Origin: Mediterranean

Description: Common crupina is a fall-germinatingannual. Its fleshy seed leaves (cotyledons) have a red orpurple midrib. The rosette leaves are obovate with entireto slightly toothed margins. Older rosette leaves andstem leaves are pinnately to bipinnately lobed withmargins armed with short, stiff spines. The alternate,stemless leaves become progressively smaller towardthe tip of the stems that grow 12 to 36 inches tall. Thestems end in 1 to several short flowering branches;additional flowering branches grow out of the upper leafaxils. One to 5 flowers are produced on each branch inJune and July. The flower heads have a narrow, cylindri-cal base (3 to 4 times longer than wide), and are toppedwith pink, lavender, or purple flowers. Each seed isencircled with a distinct ring of dark, stiff bristles near itsbroad end. It looks like a dry fly used in fishing. Seedsgerminate under a variety of temperatures and remainviable for up to 3 years. They are spread by wind, water,and wildlife.

Habitat Preferences: Common crupina is adapted to avariety of conditions, but prefers well-drained, sandy orloamy soil. It commonly infests southern slopes of steepcanyon grasslands in the Pacific Northwest, westernrangelands, and disturbed non-crop lands. Commoncrupina grows where precipitation ranges from 15 to30 inches per year and the mean annual tempera-ture is between 46° and 54° F.

Management: Common crupina is unpalatable tolivestock, so grazing is not beneficial. Because itsbristly seed can stick to their coats, livestock mayaid its spread. Repeated hand pulling, hoeing, orother tillage is effective on small infestations whendone before the plant flowers. However, mowing isnot recommended. Maintaining healthy, competitivegrasses is the best deterrent to invasion by thisweed. Herbicides are available and effective whenused correctly.

Scotch thistle AsteraceaeOnopordum acanthium L.

Mature scotch thistle plant.

Flowers are violet toreddish and thestems are winged(right).

Rosette leaves arecovered with whitehair, giving them agrayish green color(left).

31

Scotch thistleAsteraceaeOnopordum acanthium L.

Origin: Europe and western Asia

Description: Scotch thistle, a robust biennial orshort-lived perennial, may grow 10 to 12 feet tall inmoist, fertile soil, but is short and slender in dry,infertile areas. The thick seed leaves (cotyledons) aretwice as long as they are broad, with a shallow cup attheir base. The first true leaves are 3 to 4 times longerthan broad and their base clasps the crown. Unequallylong hairs form at the base of the plant. Short, stiff hairscover the upper surface of stalkless leaves, whileunderneath they have prominent veins and margins.Cottony hairs cover the developing bud, but later disap-pear. Branches on the central stem grow upright, arecovered with grayish hairs, and produce wings that maybe up to 2 inches broad and have many stiff horizontalspines. The leaves are oblanceolate, up to 12 incheslong and 4 inches broad. The margins are lobed withsharp spines. The upper surface of the leaves is green;the underside grayish. Small, lance-shaped leaves onthe upper part of the stems are often more narrow thanthe wings on the stem. The flower heads are 1 to 2inches in diameter and borne singly at the tips ofbranches from June through September. The bracts arelance-shaped; the lower ones appressed, the upperones erect or spreading, tapering to a rigid spine. Theflowers are violet to reddish. The one-seeded fruit is 1/5to 1/4 inch long, flattened, wrinkled, hairy, brownish gray toblack, and tipped with short bristles.

Habitat Preferences: Scotch thistle inhabits wasteareas, roadsides, and disturbed soils. It is oftendistributed wide and sparse, but may form impen-etrable stands.

Management: Removing plants by hand in smallareas is effective. Repeated mowing before floweringlessens seed production. Maintain healthy, competi-tive vegetation to prevent establishment. Herbi-cides are available and should be applied in therosette stage in early spring or fall.

Houndstongue BoraginaceaeCynoglossum officinale L.

Mature houndstongue plant.

In the second year,flowers produce anabundant supply ofseeds (left).

Rosettes form the firstyear of the two-yeargrowth cycle (right).

33

HoundstongueCynoglossum officinale L.Boraginaceae

Origin: Europe and Asia

Description: A biennial herb, houndstongue growsas a rosette during the first year and produces anextensive root system. The second year, it grows astalk, flowers in May through July, and produces seed inlate summer. The roundish, light green seed leaves(cotyledons) are 11/4 times as long as they are broad.They are hairless, nearly stalkless, and produce ashallow notch at their tip. The leaves from the crownhave an elongated oval shape with a lobe at their base.They grow on a long stalk covered with short hairs. Themature plant is covered with soft, matted hairs. Itsstems are stout, 16 to 24 inches tall, and producealternate, entire leaves from the base to the top. Thelower leaves are 6 to 12 inches long, 4/5 to 2 3/4 incheswide, and oblong to lance-shaped with slender stalks.The upper leaves are lance-shaped, pointed at the tip,and stalkless; the uppermost clasp the stem. Reddishpurple flowers grow from mid-June through August onnumerous, simple or branched stalks. The seed is adeeply four-lobed, prickly nutlet borne on a pyramid-shaped receptacle. Seeds cling to passing animals andare easily scattered across the landscape. The pricklyburrs may cause open wounds on animals.

Habitat Preferences: Widely distributed,houndstongue is found in irrigated and drylandpastures, fence rows, roadsides, and waste areas. Itgrows on a variety of soils from well-drained, rela-tively coarse, alkaline soils to clay subsoil.

Management: Digging, pulling, and cutting areineffective because of the extensive root system, butcan be performed on small infestations if the entireplant is removed. Clipping and mowing close to theground during flowering can greatly reduce seedproduction. Herbicides are available for houndstonguecontrol, but repeated applications are required. Thereare no biological control agents for houndstongue.

Hoary cress BrassicaceaeCardaria draba (L.) Desv.

Mature hoary cress plant.

This perennial startsgrowth very early inthe spring (right).

Small, white flowerswith four petals developbladder-like seedcapsules in mid-summer(left).

35

Cardaria draba (L.) Desv.Brassicaceae Hoary cress

Origin: Europe

Description: Hoary cress, or heart-poddedwhitetop, is a deep-rooted perennial that grows upto 24 inches tall. The leaves are 1 to 11/2 inches long,blue-green, waxy, and lance-shaped. The lower leavesare stalked, while the upper leaves are stalkless andhave two lobes that clasp the stem. Clusters of whiteflowers, each with four petals, give the plant a flat-topped appearance. Flowering occurs in spring andseeds are set by mid-summer. The heart-shaped seedcapsules contain two reddish brown seeds separated bya narrow, papery partition. Hoary cress may grow fromseed and also from root segments if the soil is tilled.Two other species, lens-podded whitetop (C.chalepensis L.) and globe-podded whitetop [C.pubescens (C.A. Meg) Jarmolenko] are common in thewestern United States. Differences in seed capsulesare used to distinguish the species.

Habitat Preferences: Cardarias commonly grow ondisturbed sites with alkaline soils. Sites susceptibleto invasion include sub-irrigated pastures, range-land, ditch banks, roadsides, and waste areas. Theyare highly competitive with other species onceestablished.

Management: Diligent digging can provide control ofvery small infestations, but requires that the entireplant be removed, including the spreading roots.Both seed and root pieces may be carried byequipment to infest new sites. Mowing reduces seedproduction and can be effective when combined withherbicides. Flooding can control the plant, but is oflimited use in dry Nevada. Sheep will graze hoarycress. There are no biological controls available.Herbicides may be effective, but require persistentapplication over several years.

Dyer’s woad BrassicaceaeIsatis tinctoria L.

Near mid-summer,purplish brown seedpods containing asingle seed appear(right).

In fall, seedling plantsbegin growing and thenoverwinter (left).

Mature dyer’s woad plant.

37

Isatis tinctoria L.Brassicaceae Dyer’s woad

Origin: Europe

Description: Dyer’s woad, a winter annual, mayflower in late April and June. It produces seed in June orearly July in northern Nevada. The seed leaves (cotyle-dons) are light green, oval-shaped, and 1/2 to 1/4 times aslong as they are broad with short stalks 1/8 to 1/4 inch long.The first true leaf is broad at the top, tapers gradually to ashort stalk, has a prominent midvein, and is smootharound the margin. The plant grows 12 to 48 inchestall with erect branches from its base. The lowerlateral branches may lie close to the ground but riseat their ends (decumbent). Dyer’s woad has a long,thick taproot that produces a new plant if cut. Thealternate leaves are bluish green, whitened with abloom (glaucous), and hairless except along themidrib of the lower leaves. The lower leaves areoblong and lance-shaped with coarsely toothedblades that narrow to a stalk nearly as long as theleaf blade, for a total length of 2 to 4 inches. Theupper leaves are smaller, narrower, and stalkless,and clasp the stem with ear-like projections (au-ricles). The yellow flowers are tiny, 1/8 inch long, andare crowded into flat-topped clusters (corymbose).The outer flower stalks are longer than the innerones. A single, yellowish seed, 1/8 to 1/7 inch long, isproduced in a purplish brown, narrow, 1/2-inch longpod.

Habitat Preferences: This plant will establish in rockysoils with minimal water-holding capacity. It infestsrangelands, grain fields, pastures, waste areas, andgrows along roadsides and fence rows. It is often aproblem in cultivated row crops and orchards.

Management: Hand pulling of individual weeds iseffective. Tilling or cultivating mature plants is notrecommended, unless done frequently. Herbicideapplication and biological control with a rust diseaseare also effective.

Perennial pepperweed BrassicaceaeLepidium latifolium L.

Dense flowerclusters appear inearly summer(right).

Mature perennial pepperweed plant.

Leaves and stemsare covered witha waxy layer (left).

39

BrassicaceaeLepidium latifolium L.

Perennial pepperweed

Origin: Southern Europe and western Asia

Description: Perennial pepperweed, or tallwhitetop, has naturalized in parts of the UnitedStates and Canada. This plant commonly grows 24 to36 inches tall, and sometimes up to 84 inches tall. Thelanceolate leaves are bright green to gray-green andhave a smooth (entire) to toothed margin. The lowerleaves are larger than the upper leaves. White flowersdevelop in dense clusters on the ends of branches.Individual flowers are very small, but the entire top of theplant blooms in early summer (June) through fall. A two-seeded fruit capsule produces reddish brown seedsthat are round, flat, slightly hairy, and about 1/16 inch long.Perennial pepperweed spreads rapidly by creepingroots to form a dense monoculture that blocks sunlightfrom the soil and suppresses the growth of other plants.

Habitat Preferences: Perennial pepperweed grows inriparian sites. It may occupy wet areas, ditches,waste places, cropland, rangeland, roadsides, andeven dry desert plant communities. It is verydifficult to control once established, especially nearwater.

Management: The robust, spreading roots andnumerous seeds make this weed difficult to control.Mechanical controls are not recommended; digging,mowing, and tilling encourage new plants to developfrom severed roots. There are no insect or diseaseagents available. However, intense, frequentgrazing by sheep that removes the plant to theground and does not let it get more than 6 inchestall all season is effective. Grazing by sheep mustbe followed up with chemical spot treatments overseveral years to eradicate this weed. Chemicalapplications must be timed properly. Integratedweed management is best; no one tool or approachused alone is successful.

Austrian fieldcress BrassicaceaeRorippa austriaca (Crantz) Bess.

Austrian fieldcress plant.

Austrian fieldcressroots (right).

Loose clusters of yellowAustrian fieldcressflowers (left).

41

Rorippa austriaca (Crantz) Bess.Brassicaceae Austrian fieldcress

Origin: Eastern Europe

Description: Austrian fieldcress is a perennial thatprimarily reproduces by rhizomes and occasionally byseed. Its smooth stems are erect and branched atthe top. It grows 12 to 36 inches tall. The leavesare alternate. The upper leaves clasp the stem andthe larger, lowermost leaves have petioles and aredistinctly toothed. The flowers are borne in looseclusters at the tips of branches from June throughAugust. Each flower has 4 small, yellow petals. Itssmall seed pods are nearly spherical or oblong with adistinct beak at the tip. Its small, brown to black, roughor warty seeds do not usually develop in northernregions and are rarely a source of reproduction or plantspread.

Habitat Preferences: Austrian fieldcress is found indisturbed and cultivated sites, roadsides, fields, andmud flats. It typically inhabits areas where the soil iswet 6 to 8 months of the year. A University of Nevada,Reno herbarium record shows that it is in Elko County,Nevada.

Management: Rotating to a cropping system thatuses less water and allows for intense cultivation anduse of herbicides is likely the most effective way tocontrol Austrian fieldcress.

St. Johnswort ClusiaceaeHypericum perforatum L.

Mature St. Johnswort plant.

Yellow flowers appearin early summer with 5petals and many showystamens (right).

The oval-shapedleaves have prominentveins and tiny trans-parent dots, visiblewhen back lit (left).

43

Hypericum perforatum L.Clusiaceae St. Johnswort

Origin: Europe

Description: St. Johnswort, or Klamath weed, is aperennial that flowers and fruits from June throughfrost. The seed leaves (cotyledons) are 1 1/2 times aslong as they are broad, with 3 veins meeting in animbedded gland at the tip. The first pair of true leavesare papery-thin with fine granules on their surface.Seedling leaves have prominent, clear dots with about 5elevated black glands along the underside of the leafmargin. Mature plants are 12 to 36 inches tall withwoody-based stems that branch on their upper halves.The root system is fibrous. Creeping horizontal stemsroot at the nodes when they touch the ground. Themature leaves are light green, stalkless, oblong or long,and narrow with an entire margin that rolls backward(revolutes). The veins are prominent underneath andsmall, transparent dots cover the 3/5 to 1 inch long and 1/12 to 1/6 inch wide leaves. Short, leafy branches areborne in the leaf axils. The dense, flat-topped flowercluster (cyme) is bright yellow. The lance-shaped sepalis 1/6 to 1/5 inch long and gradually tapers to a short point.The 3/5 to 1 inch wide flower that may have black dots onthe edge of the 5 petals, has numerous showy stamens.The seeds are borne in an oval-shaped, 3-celledcapsule, 1/6 to 1/4 inch long, that breaks apart at maturity.The shiny, dark brown or black seeds are produced inlarge quantities. They are 1/40 to 1/35 inch long and arenet-veined (reticulate).

Habitat Preferences: St. Johnswort prefers dry, sandy,or gravelly soils and often occurs in pastures, openwoods, waste places, and along roadsides.

Management: Poisonous to livestock and difficult toeradicate, St. Johnswort is controlled partially bythe Klamath weed beetle (Chrysolina quadrigenina).Selected herbicides may control St. Johnswort ifapplied correctly.

Leafy spurge EuphorbiaceaeEuphorbia esula L.

Mature leafy spurge plant.

Heart-shaped, yellowbracts surround the3-celled seed capsule(left).

Pink shoot buds growon the crown androots of leafy spurge(right).

45

Euphorbia esula L.Euphorbiaceae Leafy spurge

Origin: Eurasia

Description: This perennial grows up to 36 inchestall with long, ascending, thickly clustered stalks. Thecrown and roots are brown with numerous pink budsthat may produce new shoots. The extensive deep rootscontain large nutrient reserves that make leafy spurgecontrol extremely difficult. The alternate leaves arenarrow and 1 to 4 inches long. Those below the flowersare broadly egg-shaped and small. The flowers areyellowish green, 1/8 inch long, and arranged in clusterson the ends of stalks. A pair of heart-shaped, yellow-green bracts grow immediately below the flowers.Flowering occurs from June through September. Leafyspurge produces 1 oblong, grayish to purple seed ineach cell of a 3-celled capsule. Capsules explode upondrying, projecting seeds up to 15 feet away. The seedsare viable in the soil at least 8 years. The entire plantcontains a milky sap that may irritate the skin and eyes.

Habitat Preferences: Leafy spurge infests almost 2.5million acres in North America, mostly in southernCanada and the north-central United States. It isprimarily found in pastures, rangelands, roadsides,waste areas, abandoned cropland, and increasingly inareas disturbed by development. Leafy spurgedisplaces many species and is very difficult to controlonce established.

Management: Leafy spurge spreads by seeds orvegetative buds on root pieces brought intouninfested areas; keep it out. It causes severe mouth,throat, and digestive tract irritation and may result indeath of cattle. Sheep and goats safely eat it and can bemanaged so they prefer it to other plants, which reducesseed production. Other biological control agents mayalso reduce its stand. Fall cultivation can be helpful, butmowing, burning, and pulling are ineffective. Herbicidesare available to help control leafy spurge.

Camelthorn FabaceaeAlhagi pseudalhagi (Bieb.) Desv.

Mature camelthorn plant.

Pea-like flowers arepinkish purple tomaroon and 3/8 inchlong (left).

Spines along thestems have yellowtips (right).

47

CamelthornFabaceaeAlhagi pseudalhagi (Bieb.) Desv.

Origin: Asia

Description: Camelthorn is a perennial shrub thatgrows 18 to 48 inches tall. It is spiny and intricatelybranched. Greenish stems are ridged (striate) andhairless (glabrous), with slender spines 1 /4 to 13/4

inches long. The wedge-shaped leaves are alternatewith hairs only on the underside. They are 1/4 to 11/4

inches long and 1/8 to 1/2 inch wide. Small, pea-likeflowers are pinkish to maroon and occur on short,spine-tipped branches along the upper portion ofthe plant in June and July. The reddish brown jointedseed pods are curved upwards and deeply indented, witheach seed being clearly outlined in the pod. Camelthornreproduces primarily from deep roots and shallowrhizomes, and also by seed.

Habitat Preferences: Camelthorn grows well on dry ormoist sites and spreads rapidly along streams andcanals. It is also adapted to a wide range of soil pH;consequently, it has great potential to infest much ofthe Great Basin. It is presently growing in localizedsites in Clark County.

Management: The extensive root system makescontrol of camelthorn difficult. Tillage is ineffectiveand may increase the size of the invasion. There areno registered biocontrols, but herbicides are avail-able.

Eurasian watermilfoil HaloragaceaeMyriophyllum spicatum L.

Mature Eurasianwatermilfoil plant (left).

Eurasian watermilfoil infestation.

This aquatic plantinvades slow-moving bodies ofwater (right).

UGA1624031Alison Fox, University of Florida

49

Eurasian watermilfoilHaloragaceaeMyriophyllum spicatum L.

Origin: Eurasia, northern Africa

Description: Eurasian watermilfoil is a submersed,perennial herb. It produces an extensive, shallowroot system in the sediments of watercourses that iscapable of generating new shoots. It grows stemsand branches that are 1 to 20 feet long. Mosthowever, are 6 to 8 feet long. The branched stemsproduce four leaves at each node, but are leaflessnear their base. The nearer the stem grows to thesurface of the water, the shorter the internodes areand more branching and leaf development occurs.Thus, impenetrable mats of stems and leaves formbelow the water’s surface with a heavy infestation.The stem tips are tassel-like and reddish, especiallyearly in the season. The feather-like, pinnate leaveshave 14 or more pairs of leaflets and are 1 inch long.White to light pinkish flowers are borne bymidseason in whorls on spikes above the water. Theflower stalk may bend parallel to the water’s surface.Eurasian watermilfoil does not form turions, butreproduces by seed and vegetatively from buds,stem fragments, rhizomes, and the root crown as thestem dies back each season.

Habitat Preferences: It inhabits lakes, reservoirs,ponds, streams, and ditches where standing or slowmoving water occurs.

Management: Exclusion and boat, vehicle, andequipment cleaning and inspection prevent itsintroduction. Increasing water flow and wave actionprevents its establishment. Mechanical removal andmowing of the stem spreads this weed. However,physical removal of the root system is effective.Sterile grass carp eat Eurasian watermilfoil, butother biocontrols are not readily available. Herbi-cides are available.

Hydrilla HydrocharitaceaeHydrilla verticillata (L.F.) Royle

Hydrilla plants.

Hydrilla infests and clogs water-ways (above). It has pointedleaves borne in whorls alongeach stem (left).

UGA0002158USDA ARS Archives

UGA1148070USDA APHIS - Oxford, North Carolina Archives

51

HydrillaHydrocharitaceaeHydrilla verticillata (L.F.) Royle

Origin: Asia, Africa, Australia

Description: Hydrilla is a submersed, perennial,aquatic herb. Its small leaves are pointed andarranged in whorls of 4 to 8 along long stems. Theyhave serrated margins and 1 or more sharp teeth underthe midrib. The plant can either be dioecious (femaleand male flowers on separate plants) or monoecious(female and male flowers on the same plant). Hydrillaoften produces a mat of stems that creep above andbelow sediment of the water body and develops subter-ranean turions at their tips (tubers). Turions are whitishto brown-black, plump, ovoid tubers (potato-like struc-tures). Its flowers extend to the surface of the water on along, thread-like flower tube. The sepals and petals aretranslucent and white to reddish. Flowers occur fromJune through October. The fruits are smooth andnarrowly cylindrical. The smooth, brown seeds are notreleased from the fruits. Hydrilla reproduces by stolons(stems that grow along and above the sediment of thewater body), stem fragments, stem turions, subterraneanturions, and seeds.

Habitat Preferences: Hydrilla inhabits water 11/2 to10 feet deep and grows at water temperatures of50º to 95º F. It tolerates low light and variablewater quality, and its turions survive temperaturesnear freezing. Hydrilla can be found in freshwaterlakes, ponds, rivers, impoundments, canals, andditches.

Management: Aquatic herbicides are available forcontrol of hydrilla, but they do not affect seeds orturions, thus repeated applications are necessary.Control over small infestations can be achieved byusing an opaque fabric to block sunlight from theplants. Mechanical controls are not recommendedbecause hydrilla spreads easily by fragmentation.Grass carp effectively control hydrilla.

Mediterranean sage LamiaceaeSalvia aethiopis L.

Mediterranean sage plant.

In the first season ofgrowth, a rosettewith felt-like leavesappears (left).

The 2-lipped flowersare yellowish whiteand borne inclusters (right).

53

Mediterranean sageLamiaceaeSalvia aethiopis L.

Origin: Mediterranean, northern Africa

Description: Mediterranean sage is an aromaticbiennial that grows 24 to 36 inches tall from a stouttaproot. It appears as a large, grayish rosette inthe first season, and then matures into a multi-branched plant during the second season. The whiteto blue-green leaves are woolly and felt-like. Thelarge lower leaves have petioles and are lobed withcoarsely-toothed blades 4 to 12 inches long. Thesmaller, upper leaves clasp the stem. In time, the leavesmay lose their felt-like covering from the upper surface,exposing a green, wrinkled surface. Yellowish white,two-lipped flowers are borne in clusters of 4 to 6 onbranched stems in June and July. Four smooth nutletswith dark veins develop from each flower. Mature plantsbreak off and become tumbleweeds, easily spreadingthe seeds.

Habitat Preferences: Mediterranean sage invadespastures, meadows, rangeland, and other openareas. It grows on moderate to deep soils withgood drainage, and is well-adapted to warm, drydesert environments.

Management: Small infestations may be controlledby digging. Cutting the taproot 2 to 3 inches belowthe crown when the plants are beginning to boltprevents most resprouting. Frequent mowingduring the growing season can prevent or reduceseed production, but plants will regrow and con-tinue flowering. Mowing too late in the season, after theseed is produced, distributes the seed. Mediterraneansage is unpalatable and livestock will usually avoid it.The root-feeding weevil Phrydiuchus tau has success-fully reduced the density of Mediterranean sage in somestates when combined with competitive vegetation andwell managed grazing. Herbicides are available andare most effective when applied with a surfactant in therosette stage of the plant.

Purple loosestrife LythraceaeLythrum salicaria L.

Opposite or whorled,lance-shaped leaveshave smooth margins(right).

Showy rose-purpleflowers bloom in longvertical clusters(left).

Mature purple loosestrife plant.

55

Purple loosestrifeLythraceaeLythrum salicaria L.

Origin: Europe

Description: This introduced European ornamentalis a rhizomatous perennial that grows erect stems, often72 to 96 inches tall. The stems are stout and square orsharply angled, not round. The leaves are simple, entire,and they grow opposite each other or are whorled alongthe stem. These lance-shaped leaves have smooth(entire) margins and are stemless. Rose-purple flowershave 5 to 7 petals and are arranged in long, verticalracemes (linear clusters) at the end of the stems. Theyare very showy mid-summer to fall. The small seeds,less than 1/16 inch, are dark. This is an aggressive weedin moist sites because of its stout roots and its ability tospread and propagate from seed and rhizomes.

Habitat Preferences: Purple loosestrife readilyinfests aquatic sites—streambanks, shorelines ofshallow ponds, reservoirs, canals, and ditches. Itimpedes water flow and greatly reduces habitat forwildlife. It usually occupies moist or marshy sites,but once established tolerates intermittently drysoils.

Management: Many states besides Nevada havedeclared purple loosestrife a noxious weed. The NevadaDepartment of Agriculture has required nurseries stopselling purple loosestrife and its cultivars as ornamen-tals. Eradication of purple loosestrife may be possible insmall infestations. Several herbicides are available forchemical control. It is difficult to get all of the roots andstems when removing the plant by hand, but this methodcan be used for small infestations. Cutting and mowingcan spread the plant and are ineffective. Burning isdifficult and favors loosestrife over native plants. Burningpurple loosestrife is not recommended. Flooding mayenhance its spread and should not be used. There areseveral biological control species available to containpurple loosestrife.

Green fountain grass PoaceaePennisetum setaceum (Forsk.)

CDFAJ.R. Manhart

Fountain grass flower, purple cultivar.

Mature fountain grass plantsmay have green or purpleseedheads.

UCCEJoe DiTomaso

57

Green fountain grassPoaceaePennisetum setaceum (Forsk.)

Origin: Africa

Description: Green fountain grass is a showy peren-nial. Its blades are rolled in the bud. They grow foldedor flat, are smooth (glabrous) to sparsely short-hairy,and have pronounced midveins on their underside.The ligule consist of a fringe of white hair. It lacksauricles and its collar margins are hairy (ciliate) withwhite hair. Its roots are fibrous. Below eachspikelet or small cluster of spikelets are long,flexible bristles. The green to purplish (associatedwith purple cultivars), lance-shaped spikelets consistof a lower glume-like sterile floret and an upperfertile floret. Its seeds are oblong to obovoid, yellowishbrown, and smooth. Reproduction is by seeds dis-persed by spikelets in late spring through summer.

Habitat Preferences: Fountain grass prefers dis-turbed sites, roadsides, undisturbed coastal dunes,coastal sage scrub, warm desert shrubland, andcanyons. It is planted in urban landscapes. It growsbest in areas with mild winters and some summermoisture. It tolerates periods of drought, lightshade, and most soil types, but does not surviveprolonged periods of freezing temperatures. It cangrow in rock crevices and pavement cracks, butcannot tolerate saline conditions. It has great abilityto adapt to an environment, which increases itsability to spread.

Management: It is most important to control seedproduction. Hand removal of small infestations canhelp prevent its spread. Mowing and grazing arenot recommended as they increase stand density inthe long run. Also, cattle do not prefer fountaingrass and eat it only after they have depletedsurrounding native species. Do not burn fountaingrass because it is fire-adapted, growth is stimu-lated, and stands increase with fire. Nonselectiveherbicides are available to kill it. Both pre- andpost-emergent products are recommended whereseed has dispersed.

Medusahead PoaceaeTaeniatherum caput-medusa (L.) Nevski

Twisted awns or beards area characteristic used toidentify medusahead (left).

Medusahead is a highlycompetitive plant thatcrowds out all othervegetation on infestedrangeland (right).

Mature medusahead plant.

59

MedusaheadPoaceaeTaeniatherum caput-medusa (L.) Nevski

Origin: Eurasia

Description: This aggressive winter annual may grow6 to 24 inches tall. The leaf blades are usually 1/8

inch wide or less and rolled when cut in cross-section. The inflorescence is a long-awned spikethat is nearly as wide as it is long. The mature awnsare twisted, stiff and finely barbed, and range from1 to 4 inches long. Flowering and seed formationoccur in May and June. After the florets fall away, abristly head of awn-like glumes persists, often overwinter. Medusahead may be confused with foxtailbarley and squirreltail. However, its spike does notbreak apart as the seeds mature, and it is an annualwhile they are perennial plants. Likewise,medusahead seedlings are similar to downy bromeseedlings, except the latter is much hairier.

Habitat Preferences: Medusahead infests semi-aridrangeland and has invaded millions of acres in thePacific Northwest, northern California, and is nowspreading across northern Nevada. It grows wherethe annual precipitation is 10 to 40 inches duringfall, winter, and spring. Lack of summer precipita-tion favors medusahead. In the Great Basin, infesta-tions primarily occur in former sagebrush-grass orbunchgrass communities that receive 10 to 20inches of precipitation. It does best in clay soils thatshrink, swell, and crack. It is extremely competitive,crowding out even such undesirable species asdowny brome (approximately 9 million acres inNevada).

Management: Control of small isolated infestations iscritical to reducing the impact of medusahead onGreat Basin rangelands. Spring plowing after mostof the medusahead has germinated has given somecontrol, and disking can be used as a follow-up.Combining mechanical efforts with burning or herbi-cides will provide better results. Revegetation andcareful grazing management must follow any controleffort to prevent medusahead from reestablishingdominance.

Sulfur cinquefoil RosaceaePotentilla recta L.

Light yellow flowershave 5 deeply notchedpetals and yellowcenters with manystamens (left).

Each compound leafhas from 5 to 7 toothedleaflets (right).

Mature sulfur cinquefoil plant.

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Sulfur cinquefoilRosaceaePotentilla recta L.

Origin: Europe

Description: Sulfur cinquefoil is easily confused withnative Potentilla species and its identification shouldbe confirmed by a plant specialist. It is an attractiveperennial that grows 12 to 24 inches tall. It pro-duces well-developed rootstocks. The leaves arepalmately compound with 5 to 7 toothed leafletsradiating out from the leaf stalk. The leaves are greenon their underside rather than silvery as in manyPotentilla species. The leaves and stems aresparsely hairy. The light yellow flowers have 5petals and each petal is notched at the end. Thecenter is yellow and has numerous (30) uprightstamens. Each flower produces numerous roundseeds (achenes). Flowering occurs from May to July.

Habitat Preferences: Sulfur cinquefoil grows in dis-turbed areas and roadsides, as well as in rangelandwhen moisture is available. It is not a weed ofcultivated crops. Colonies of plants may also infestundisturbed sites. It is not limited by soil texture.

Management: Control is very difficult. Hand digging canbe effective in small infestations. Tilling, cultivation, andmowing are not effective. Selective herbicides are themost effective tool for controlling larger infestations.Sulfur cinquefoil is unpalatable to most livestock, andmost grazing practices accelerate its dominance.

Giant salvinia SalviniaceaeSalvinia molesta Mitch

Giant salvinia plant.

Giant salvinialeaves floating inwater (right).

Giant salvinia hairsform an eggbeatershape (left).

UGA0002106Mic H. Julien

UGA1317055Scott Bauer

UGA0001090Scott Robinson

63

Giant salviniaSalviniaceaeSalvinia molesta Mitch

Origin: Southeastern Brazil

Description: Giant salvinia is a floating, rootless,aquatic fern with horizontal stems that float justbelow the water’s surface. A pair of green, floating oremergent, ovate to oblong leaves are produced at eachnode. They may be 1/2 to 11/2 inches long. They arecovered with tiny, white, water-resistant hairs on theupper surface. The stalks of each hair is dividedinto 4 thin branches that rejoin at the tips to form a cagethat resembles a tiny eggbeater. The cage-like hairsmay be damaged on mature leaves, but should benoticeable on young leaves. Giant salvinia also has ahighly-divided third leaf that is brown and danglesunderwater. It is often mistaken for a root. Giant salviniagrows rapidly to form thick mats with more vertically thanhorizontally aligned leaves. This plant’s egg-shaped,slender, pointed sporocarps are used to distinguish itfrom related species. These sporocarps develop inelongated chains among the submersed leaves. Giantsalvinia reproduces very effectively through vegetativemeans.

Habitat Preferences: Giant salvinia infests freshwa-ter lakes, ponds, oxbows, ditches, slow-flowingstreams and rivers, marshes, and rice fields. It hasgreat potential to foul irrigation systems. It cansurvive freezing temperatures, but not icy waters. Itcannot live in brackish waters and dies when the saltlevel exceeds 1/3 that of sea water, 34 ppt (parts perthousand).

Management: Mechanical methods can be used toremove small infestations of giant salvinia, but allfragments must be removed from the water and burned.The salvinia weevil and salvinia stem borer may be usedfor biological control, and are considered to be verysuccessful. Herbicides are also available for chemicalcontrol.

Dalmatian toadflax ScrophulariaceaeLinaria dalmatica (L.) Mill.

Mature dalmatian toadflax plant.

Yellow flowers with longspurs appear in mid-summer (left).

Early spring growth haswaxy leaves with a blue-green color. Leavesindividually grasp thestem (right).

65

Linaria dalmatica (L.) Mill.Scrophulariaceae Dalmatian toadflax

Origin: Southeastern Europe

Description: Dalmatian toadflax is an aggressiveperennial that grows up to 36 inches tall. It repro-duces by seed and deep roots. The egg-shaped leavesare dense and grow alternately along the stem. Theyhave a smooth edge (entire), are waxy, gray-green, andclasp the stem. The upper leaves are conspicuouslybroad-based. Showy flowers are borne in the axils ofupper leaves and are 2-lipped, 3/4 to 11/2 inches long.They have a long spur and are yellow with an orange,bearded throat. The fruit is a 2-celled capsule about 1/4inch long with many irregularly-angled black seeds.Flowering occurs from mid-summer to early fall.

Habitat Preferences: Dalmatian toadflax primarilyoccurs on sandy or gravelly soils along roadsides,railroads, pastures, cultivated fields, and on range-lands and clearcuts. It can adapt its growth to fit arange of habitats, and is tolerant of low tempera-tures and coarse-textured soils. It is highly competi-tive in areas where summers tend to be dry.

Management: The extensive, deep root systemcombined with the waxy leaves that repel pesticidesmake this an extremely difficult plant to control. Handpulling dalmatian toadflax can be effective for smallinfestations, particularly in sandy soils or when soils aremoist. Hand removal must be repeated over severalyears in order to deplete the root system. Mowing is notrecommended, but frequent cultivation will controltoadflax. Spring grazing by cattle increases stands oftoadflax, but grazing by sheep reduces the infestationsize and limits seed production. There are severalspecies of insects that have been used for biologicalcontrol of dalmatian toadflax. Effectiveness of herbicidesin controlling dalmatian toadflax is highly variable, partlydue to its waxy leaves. Soil type affects the effectivenessof pre-emergent herbicides. Dalmatian and yellowtoadflax hybridize. Unfortunately, herbicide effec-tiveness may be reduced in hybrids.

Yellow toadflax ScrophulariaceaeLinaria vulgaris (L.) Mill.

Mature yellow toadflax plant.

Narrow leaves arepointed at both endsand individuallyconnected to the centralstem (left).

Snapdragon-like,yellow flowers have anorange throat andspur-like tail (right).

67

Linaria vulgaris (L.) Mill.Scrophulariaceae Yellow toadflax

Origin: Eurasia

Description: Yellow toadflax is a creeping perennialthat grows 12 to 24 inches tall. It has several mainstems with numerous leaves that are pale green,narrow, pointed at both ends, directly attached tothe stem, and 2 1/2 or more inches long. The attractiveyellow flowers are 1 inch long with a bearded, orangethroat and a spur-like tail. Several form near the ends ofthe stalk from May through September. The fruit isround, 1/4 inch in diameter, 2-celled, and brown, withmany seeds. The seeds are dark brown to black, 1/12

inch in diameter with a flattened, papery, circular wing.Yellow toadflax reproduces by seed and undergroundroots. Along with the seed produced, the extensive rootsystem makes this plant difficult to control.

Habitat Preferences: Yellow toadflax is an aggressiveinvader of rangelands where it displaces desirablegrasses. It is also found along roadsides, in wasteplaces, and cultivated fields.

Management: Hand pulling yellow toadflax can beeffective for small infestations, particularly in sandysoils or when soils are moist, but must be repeatedover several years in order to deplete the root system.Mowing is not recommended, but frequent cultiva-tion will control toadflax. Grazing cattle on yellowtoadflax increases the infestation, but grazing bysheep reduces the stand size and limits seedproduction. There are several species of insectsthat biologically control yellow toadflax. Effective-ness of herbicides is highly variable due to its highgenetic variability and herbicide resistance. Soiltype is important when applying pre-emergentherbicides to contain or control yellow toadflax.Hybrids between dalmatian and yellow toadflaxdemonstrate less response to herbicides.

Saltcedar TamaricaceaeTamarix ramosissima Ledeb. & Tamarix spp.

Mature saltcedar plant.

Flowers are pink, small,5-petalled, and borne infinger-like clusters (left).

Smooth woody stemsare dark brown toreddish brown (right).

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Tamaricaceae Saltcedar

Origin: Turkey, Iran, central Asia, China, and Mongolia

Description: This deciduous shrub and small treegrows 5 to 20 feet tall. Bark on saplings and youngbranches is reddish brown, turning gray, and becomingfissured with age. The pale blue-green leaves are smalland scale-like, have a smooth (entire) edge, and areborne alternately on highly branched, slender stems.Flowers are pink to white, may occur in spring throughlate summer, and usually have 5 petals. Smallflowertamarisk (T. parviflora DC.) is similar in appearance, buthas 4-petalled flowers with brown to deep purple bark onthe stems. Smallflower tamarisk was introduced fromsouthern Europe and is also widespread. Several otherspecies of tamarisk have naturalized across the UnitedStates as well.

Habitat Preferences: Saltcedar has infested the desertsouthwest, mostly along waterways and in arroyoswith ephemeral flows, interrupting natural habitats.It is well adapted to alkaline and salty soils, heatand cold, and windy sites. Its aggressive, deeproot system uses much ground water, often to thedetriment of other species. In many sites, it forms apure stand that is almost impenetrable. Few to noplants grow under its canopy because of the highconcentrations of salt that builds up in the soil fromits accumulated leaf litter and the excretion of saltfrom glands on the leaves. Thus, with time, itchanges the soil chemistry and reduces competition.

Management: Plowing, cutting, mowing, chaining,and burning are ineffective methods for controllingsaltcedar. Flooding saltcedar for 1 or 2 years iseffective if the water covers the tree or shrub.Herbicides are available for control, but saltcedarshould not be disturbed for 2 years after application.This allows time for the chemical to move throughoutand kill the root system. A mealy bug and a leaf beetleare available for biological control depending on theclimatic and environmental conditions at the site.

Tamarix ramosissima Ledeb. & Tamarix spp.

African rue ZygophyllaceaePeganum harmala L.

Mature African rue plant.

Leaves are finelydivided in longsegments and theflowers have 5, whitepetals (left).

The green fruit ofAfrican rue containsmany small seeds(right).

71

African rueZygophyllaceaePeganum harmala L.

Origin: North Africa, Asia

Description: African rue is a multi-branched, perennialherb. It has short, creeping, horizontal roots and deepspreading roots that can grow over 20 feet deep inextremely dry soils. The plant usually does not grow over24 inches tall and 36 inches wide. Its smooth, alternateleaves are finely and deeply divided with long, narrowsegments. The flowers are borne on stiff stems fromlate spring through early fall and have 5, white petalswith a yellow center. Many small seeds are produced ina green, 3-chambered fruit. African rue is poisonous tocattle, sheep, horses, and to humans. The mostpoisonous parts are the seeds, fruit, and youngleaves. It reproduces primarily by seeds, but rootscan produce new shoots.

Habitat Preferences: African rue grows in veryalkaline, salty soils with little rainfall, and is well-adapted to arid climates. It is found in dry placessuch as roadsides, abandoned fields, gravel pits,and corrals. It has begun to spread in Mineral andChurchill counties in Nevada. It has also been foundin California, Arizona, New Mexico, Idaho, Oregon,Washington, and western Texas.

Management: Maintaining a healthy plant commu-nity helps prevent African rue establishment.Mechanical control by mowing, cultivation, or burningis usually unsuccessful because the plant resproutsfrom the crown and lateral roots. These actionsspread African rue. Continuously hand pullingseedlings or young plants may be effective. Africanrue is unpalatable and poisonous, so grazing is notrecommended as a control measure. No biologicalcontrol agents are available in the United States forAfrican rue. Herbicides are available and should beapplied repeatedly over several years to obtaincontrol. After control is obtained, desirable vegeta-tion should be established to prevent its re-invasion.

Syrian Beancaper ZygophyllaceaeZygophyllum fabago L.

This plant has spread-ing roots that canproduce new plants ifdisturbed (right).

Syrian beancapergrows to 36 inchestall and has thick,waxy leaves (above).

Syrian beancaper is well-adapted to deserts.

73

Origin: Asia

Description: Syrian beancaper is a perennial herbor forbe that produces a taproot when grown from aseed, and then develops a spreading root system. Newplants develop from the spreading roots. Each year,coarse, thick stems are produced from the crown thatbecome semi-woody before they die from cold weather.The rounded plant grows to 36 inches tall. The smooth,opposite leaves are thick, waxy, fleshy, and oblong-shaped. White to cream-colored flowers have a pinkishtinge, 5 petals, and are borne on the end of a long stalk.Each flower produces 10 long, showy, orange stamens.The fruit is an oblong, 5-sided cylinder with 5 chambersthat contain a single seed each. Syrian beancaperreproduces by seed, spreading roots, and root pieces ifthe root system is disturbed by tillage or other damagingactivities.

Habitat Preferences: This plant invades disturbedsoils along roadsides, in corrals, around gravel pits,and construction sites. It is well-adapted to desertconditions including infrequent precipitation,drought, alkaline soils, and even saline soils.

Management: Mechanical disturbance of the rootsystem, such as tillage and cultivation, will spreadthis weed unless frequently applied to exhaust thestored food reserves. Frequent hand pulling willcontrol a young, small infestation. Mowing andburning to prevent viable seed production mayweaken the plant and slow its spread, but the plantwill resprout and can spread by the roots. Biologicalcontrol is not available. Herbicides are most effec-tive when surfactants are used because of the waxyleaves.

Syrian BeancaperZygophyllaceaeZygophyllum fabago L.

Glossaryachene: a small, dry, hard, indehiscent, 1-seeded fruit.acute: sharp-pointed.alkaloid: bitter, colorless, organic compounds (bases) found

in numerous plants; many are poisonous if ingested.alternate: leaf structure not opposite or whorled on stem.annual: completing the life cycle in 1 growing season.apical: situated at the tip.appressed: pressed flat against another organ.ascending: rising obliquely or curving upward.auricle: an ear-shaped appendage.awn: a terminal, slender bristle on an organ.basal: relating to, or situated at the base.beak: a prolonged firm tip, particularly of a seed or fruit.bearded: bearing long stiff hairs.biennial: completing the life cycle in 2 growing seasons.bract: a reduced leaf subtending a flower.bud: an undeveloped stem, leaf, or flower.calyx: external, usually green, whorl of a flower, contrasted

with the inner showy corolla (petals).capsule: dry, dehiscent fruit composed of more than 1 carpel.ciliate: fringed with hairs on the margin.corolla: collectively the petals of a flower.cotyledon: the primary leaf or leaves of the embryo.creeping: to grow along the ground or some structure.crown: the persistent base of an herbaceous perennial.dehiscent: opening spontaneously when ripe to release the

contents, as an anther or seed vessel.dentate: having the margin cut with sharp teeth.dioecious: flowers unisexual, the male and female flowers

occur on different plants.divided: said of leaves; deeply lobed, the sinuses extending to

the base of the leaf or midrib.entire: margins smooth without teeth or lobes.ephemeral: lasting for a day or less.flower: seed-producing structure of a plant.fruit: ripened ovary and its associated structures that enclose

it at maturity.glabrous: smooth, no hairs present.glandular: bearing glands; glandular hairs have glands or a

sticky substance at the end.glaucous: covered or whitened with a bloom.glumes: chaff-like bract; used for the 2 lower empty bracts of

a grass spikelet.habitat: the normal situation in which a plant lives.herb: a plant without persistent woody stem, at least above

ground.

75

herbaceous: pertaining to an herb; leaf-like in color andtexture; a non-woody plant; dying to the ground each year.

hybrid: a cross between two species.indehiscent: not splitting open, as an achene.inflorescence: flowering part of a plant; generally used for

flowering cluster.involucre: a whorl of bracts (phyllaries) below a flower

cluster, as in the flower heads of the Composite family.lanceolate: lance-shaped; several times longer than wide,

broadest toward the base and pointed at the apex.lateral: borne on the side of a structure or object.leaf: flat thin part of a plant growing from the base or stem.lemma: in grasses, the lower of the 2 bracts immediately

enclosing the floret.ligule: the strap-shaped part of a ray flower in the Composite

family; the thin, collar-like appendage on the inside of theblade at the junction with the sheath in grasses.

linear: narrow and flat with sides or edges parallel as in aleaf.

lobed: bearing lobes; generally the sinuses are not halfwayto the base of leaf or midrib, as in oak leaves.

midrib: the middle vein of a leaf.monoculture: only one species present.monoecious: having male and female flowers on the same

plant.node: the joint of a stem where a leaf originates.oblanceolate: inversely lanceolate.oblong: 2 to 4 times longer than wide with the sides nearly

parallel as in a leaf.obovate: inversely ovate.ovate: shaped like a hen’s egg in longitudinal section.ovoid: solid ovate or solid oval.palmate: in a leaf, having the lobes or divisions radiating

from a common point.pappus: a crown of bristles or scales on an achene.perennial: a plant whose life cycle extends for 3 or more

years.persistent: remaining attached after like parts normally fall

off.petal: 1 of the leaves of a corolla.petiole: a leaf-stalk.phyllary: the name of the bract on the head of a sunflower.pinnate: compound leaf with leaflets arranged on each side

of a common petiole.prostrate: lying flat upon the ground.protrusion: a part of a structure that sticks out.

pubescent: covered with hairs; generally short, soft hairs.raceme: a simple, elongated, indeterminate inflorescence.ray flowers: generally the showy, strap-shaped flower as in

the head of a sunflower; as opposed to the less showy diskor tube flower.

recurved: curved outward, downward, or backward.rhizomatous: stem growing laterally partly or wholly beneath

the soil.root: the portion of the plant, generally below ground, that

anchors the plant and absorbs moisture and nutrients fromthe soil.

rosette: dense, basal cluster of leaves arranged in a circularfashion about one point, usually at ground level.

seed: that part of the plant containing the mature embryofrom which a new plant can grow.

sepal: a leaf or segment of the calyx.serrate: with sharp teeth directed forward; often said of leaf

edges.sessile: without a stalk of any kind; said of a leaf or flower

coming right off of a stem.simple: of only one part; not divided into separate segments;

not compound.spine: a sharp-pointed, stiff, woody tissue.spore: the reproductive body of lower plants, analogous to

the seed.sporocarp: a receptacle containing spores.stamens: one of the pollen-bearing organs of a flower; male

part; made up of filament and anther.stem: the main stalk of a plant; supports leaves, flowers

and fruit.stolon: horizontal or creeping stem that roots at its nodes or

tip producing a new plant.striate: marked with longitudinal lines or furrows.taproot: a primary stout vertical root giving off small

laterals but not dividing.terminal: of, or at the end of something.toothed: a small marginal lobe; as on a saw, dentate.trichome: plant hairs borne on leaves and stems.tuber: a thickened, solid, and short underground stem with

many buds.turion: tuber-like tissue of aquatic plants.venation: the arrangement of the veins of a leaf.whorled: with 3 or more leaves or other structures growing at

a node arranged in a circle around a stem.wings: thin expansions bordering or surrounding a stem.winter annual: an annual plant that germinates in the fall,

completing its life cycle the following year.

Common NameAfrican RueAustrian fieldcressCamelthornCanada thistleCommon crupinaDalmatian toadflaxDiffuse knapweedDyer’s woadEurasian watermilfoilGiant salviniaGreen fountain grassHoary cress/WhitetopHoundstongueHydrillaIberian starthistleLeafy spurgeMalta starthistle/ TocaloteMediterranean sageMedusahead

Musk thistle/ Nodding thistlePerennial pepperweed/ Tall whitetopPurple loosestrifePurple starthistleRush skeletonweedRussian knapweedSaltcedar/TamariskScotch thistleSpotted knapweedSquarrose knapweed

St. Johnswort/ Klamath weedSulfur cinquefoilSyrian beancaperYellow starthistleYellow toadflax

Botanical NamePeganum harmalaRorippa austriacaAlhagi pseudalhagiCirsium arvenseCrupina vulgarisLinaria dalmaticaCentaurea diffusaIsatis tinctoriaMyriophyllum spicatumSalvinia molestaPennisetum setaceumCardaria drabaCynoglossum officinaleHydrilla verticillataCentaurea ibericaEuphorbia esulaCentaurea melitensis

Salvia aethiopisTaeniatherum caput-medusaeCarduus nutans

Lepidium latifolium

Lythrum salicariaCentaurea calcitrapaChondrilla junceaAcroptilon repensTamarix ramosissimaOnopordum acanthiumCentaurea maculosaCentaurea virgata spp. squarrosaHypericum perforatum

Potentilla rectaZygophyllum fabagoCentaurea solstitialisLinaria vulgaris

Index of five digit plant codes from theWeed Science Society of America:

PlantCodePEGHARORAUALHPSCIRARCJNVULINDACENDI

ISATIMYPSPSAVMOPESSA

CADDRCYWOF

HYLLICENIBEPHES

CENME

SALAEELYCM

CRUNU

LEPLA

LYTSACENCACHOJUCENRETAARAONRACCENMACENSQ

HYPPE

PTLRCZYGFACENSOLINVU

Nevada Cooperative WeedManagement Area Groups

9/2003

Alpine County/Upper Carson WatershedCarson CityChurchill CountyClark CountyClark County MSHCP Weeds Working GroupElko CountyGerlachHumboldt WatershedHumboldt County Task ForceLander County Weed TeamLas Vegas WashLincoln CountyLong Valley/NewarkLower TruckeeRailroad ValleySouthern Nye CountySpring Creek RegionStorey CountySurprise ValleySpecial Weed Action Team (Susanville)Tahoe Basin Weed Coordinating GroupTri-CountyTruckee MeadowsWalker River BasinWashoe ValleyWest Central Lyon CountyWhite River Valley

If you are interested in forming a cooperative weedmanagement area working group, or you want to contactone of the cooperative weed management area groupslisted above, call (775) 688-1182 ext. 269.

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All photographs are courtesy of Weeds of the Westexcept for the following:

Fountain grass flower, full plants, and flower spikephotographs, Austrian fieldcress photographs, andhydrilla leaves and infestation photographs arecourtesy of the California Department of Food andAgriculture, http://pi.cdfa.ca.gov/weedinfo/Index.html.

Fountain grass single plant photograph is courtesy ofJoe DiTomaso, Weed Specialist, University of CaliforniaCooperative Extension.

Hydrilla growing tip image: USDA ARS Archives, USDAARS, Image 0002158. Hydrilla plant image: USDAAPHIS, Oxford North Carolina Archives, Image 1148070.Eurasian watermilfoil image: Fox, Alison. University ofFlorida, Image 1624031. Giant salvinia images:Bauer, Scott. USDA ARS, Image 1317055; Julien, Mic H.Commonwealth Scientific and Industrial ResearchOrganization, Image 0002106; Robinson, Scott. GeorgiaDepartment of Natural Resources, Image 0001090.ForestryImages.org, http://www.forestryimages.org/.

Other Eurasian watermilfoil photographs are courtesy ofDave Spencer, USDA Exotic and Invasive Weeds Re-search Unit, Davis, CA.

Syrian beancaper photographs are courtesy of Jason C.Davison, Area Extension Specialist, University of NevadaCooperative Extension.

Malta Starthistle photographs courtesy of New MexicoState University Cooperative Extension Service.

References:

Weeds of the West. 2000. T.D. Whitson, Ed. WesternSociety of Weed Science in cooperation with theWestern United States Land Grant UniversitiesCooperative Extension Services, Newark, CA.

The Grower’s Weed Identification Handbook. 1992.University of California, Division of Agriculture andNatural Resources, Oakland, CA. Publication 4030.

The University of Nevada, Reno is an equal opportunity/affirmitiveaction employer and does not discriminate on the basis of race, color,religion, sex, age, creed, national origin, veteran status, physical ormental disability, or sexual orientation in any program or activityit operates. The University of Nevada employs only United Statescitizens and aliens lawfully authorized to work in the United States.

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