Invasive Plants:the Increasing Threat to Habitat & Biodiversity

Tonight’s Outline

• Weeds & Lists

• Impacts

• Resources

• Specific Weeds & Management

• Manual, mechanical, chemical

Chemical Option: Herbicides

• Know your target weed first

• Read label before you purchase

• Follow the label (it’s Federal Law)

• Timing is crucial for success

• Using the labeled rate is crucial too– Follow rate recommendations

– MORE IS NOT BETTER • MORE can actually make the treatment LESS effective

• Rates in presentation expressed as %– Ex: 128 oz/gal (water)

128 x .01 (1%) = 1.28

– 1% rate =1.28 oz herbicide/gal of water

– 2% rate (128 x .02) =2.56 oz herbicide/gal of water

– 5% rate (128 x .05) = 6.4 oz herbicide/gal of water

(1 oz = 2 Tablespoons)

• Washington State Weed Law (RCW 17.10)

• Washington State Noxious Weed List

(WAC 16-750)

• Requires the landowner to control or manage listed noxious weeds

• County weed coordinator ensures that landowners control their weeds

*also a legal term in Washington

Noxious (nok´shəs). adj. 1.Harmful or

injurious to health or physical well-being*

The 3 Classes of Noxious Weeds

Class A Noxious Weeds are limited in their

distribution throughout Washington State,

High Priority.

Goal – Eradication/Prevention of new

Class B Noxious Weeds are limited in their

distribution to parts of Washington State

Goal – Containment/Prevention of seedfall.

Can be Designated by the state for control in

specified counties or regions

Class C Noxious Weeds are widespread in

Washington State

Goal – Containment as required by county

sometimes through special interests such as

the agriculture industry

Giant

Hogweed

Himalayan

Blackberry

Purple

Loosestrife

Washington’s Noxious Weed Lists

• 2018 Washington State Noxious Weed List –

established plants which need management or

eradication in Washington State (chosen through

annual review and public hearing)

153 plant species

2018 Whatcom County Noxious Weed List

Selected annually through public hearing process

123 plant species

• Washington State Monitor List (Non-Regulatory) – “suspect”

weeds for information gathering

43 plant species

• Washington’s Prohibited Plants List – plants/plant parts cannot be

bought, sold or transported

86 plant species

THESE LISTS ALL INCLUDE DIFFERENT PLANT SPECIES

Over half of the listed noxious

weeds in Washington State

were first introduced as

garden ornamentals

What is a Weed?

• A plant out of

place

• “...a plant whose

virtues have not

yet been

discovered.”

-Ralph Waldo Emerson

Competitive Abilities

• abundant reproduction

• means of seed dispersal

• Rapid growth from seed,

rhizomes, stolons etc.

• seed longevity

• adaptability to wide range

of conditions

• allelopathic

• thrive in disturbed soil

Weed Life CyclesAnnual Biennial Perennial

1-year life cycle 2-year life cycle Multiple year life cycle

Easiest to work with A little more difficult Most difficult

Spread by seed (prolific) Spread by seed Spread by seed, roots, fragments, tubers, etc.

Summer or winter seeding Rosette plant 1st year

Flower/seeds 2nd year

Can behave like perennial

Bittercress BindweedBull Thistle

Identification

• The most important first step

Bull Thistle Canada Thistle

Which Thistle is Which?

Canada ThistleCirsium arvense

Rhizomes (creeping roots)

Bull ThistleCirsium vulgare

Tap Rooted

Himalayan BlackberryRubus armeniacus

Class C

• Native to Western Europe

• Reproduces by seed and

by canes rooting in the

ground

• Very aggressive growth

• Hand-grubbing – get all of the

roots

• Mowing repeatedly

• Goats

– They can mow plants back so

access to the roots is easier for

digging

• Herbicide

– Foliar Spray: 1-1.5%

glyphosate in the fall (1.3-1.9 oz concentrate /gal water)

Management Options

Disposal Options:

• Move to impervious areas to dry out and then haul away

• Bag and haul

• Do not compostFlorafinder.com

• Produces up to 12,000 seeds per

plant per year

• Seeds can be flung 10-15 feet by

ripe exploding pods

• Seeds can lie dormant from 5 - 30

years

• Scotch broom pollen is not a likely

source of common allergies

Scotch BroomCytisus scoparius

Management Options

• Weed Wrench™/ Extractigator™• soil disturbance can sometimes

cause dormant seeds to germinate

• Cut stem and girdle

good for places where erosion is

a concern

•Herbicide–Triclopyr – cut stump treatment

– Glyphosate – 1.5-2% in the spring(1.9-2.5 oz concentrate/gal water)

• 13-petaled yellow flowers

• Leaves have wavy margins

• spreads by seed (wind)

• contains alkaloids toxic to

livestock

Tansy Ragwort

Senecio jacobaea

Class B

Management Options

• Hand-pulling

– at bolting stage

– can clip heads if blooming and bag

up

– DO NOT leave blooming/pulled

plants to dry out in the open

• Herbicide– 2,4-D (many brand names)

– 2,4-D/Triclopyr (Crossbow, etc.)

– 2,4-D/Dicamba (WeedMaster, etc)

• spring or fall timing is best• follow label rates

• spray to wet

• Mowing not recommended

Common Tansy

St. Johnswort

Not to be confused

with...

• From residences, moving into natural areas

• spreads by seed (birds) and creeping roots

• Adds enormous weight loads to trees once established, increasing tree/property damage

• Also crowds out understory shrubs/plants

• Plants mature and produce seed in 8-9 years

• Attracts rats and rot

English/Atlantic/Irish IvyHedera sp.

Class C

mature

seed

1st year seedling

Management Options

•Hand-pulling, grubbing, mowing

regularly, rolling for ground level

sites

• Mulching – 8 inches of material

• Cutting for trees

• HerbicideGlyphosate

– Foliar: 2-4%, surfactant is important

– leaf treatment to open waxy surface

– Basal treatment: spray base of plant

with 33% solution

– Cut Stem: cut stem and treat

immediately with herbicide

Cutting at Ground and Shoulder Level

Bohemian KnotweedPolygonum x bohemicumClass B/Prohibited Plant List

• Hybrid of Japanese and

Giant Knotweed

• Hollow jointed stem

• White flowers in late

summer (bees love it)

• Extensive, fleshy roots

• Spreads primarily through

root/plant fragments, but

also by seed

• Can grow through asphalt

and survive in marine

intertidal areas

• Leaf litter from knotweed very low in nitrogen

• Alters food web in riparian areas by decreasing native

leaf litter by as much as 70%• Foliar/Bending (large

monocultures)

– 3-5% glyphosate

– And/Or .05 -1.0% imazapyr

– Optional June/July bending

– August thru October foliar

applications

• Injection (isolated patches)

– 5 ml of 100% glyphosate per

stem

– Removal by digging

recommended only for patches

< 1 meter in diameter.

Management Options

English HollyIlex aquifolium

Monitor List (non-regulatory)

• Toxic to humans

• Invades native forest

• Water glutton

• Extremely difficult to manage

when it matures (to 50 feet tall)

Management Options

• Hand Pulling– Remove small seedlings

– Repeated cutting of larger

plants for suppression

• Herbicide– Glyphosate, Imazapyr,

Triclopyr

– Cut stump

– Frill cut

– Follow label instructions for rate

Yellow ArchangelLamiastrum galeobdolon

Class B-Designate/Prohibited Plant List

• native to Europe

• introduced as a

garden ornamental

and groundcover

• very invasive,

spreading both by

seed and by

runners

• often spread by

yard waste dumping

• now banned from

sale in Washington

Management Options

• Hand Pulling

– remove all plant parts and bag

for disposal

– No composting

– Can mulch to help hand pulling

• Regular and careful mowing

• Sheet mulching

– layers of newspaper/cardboard

with 3-4 inches of mulch on top

• Herbicide–Triclopyr, Metsulfuron (Escort ™), Imazapyr

(Polaris™, Habitat™)

– select carefully and follow label rates

Spurge LaurelDaphne laureola

Class B

• Evergreen shrub about 4 fttall

• Looks like a rhododendron but without showy flowers

• Flowers are very small and green

• Black, shiny berries

• All parts of the plant are poisonous and can cause severe skin and eye irritation

Management Options

• Hand Pulling

– Wear protective clothing and eye

protection

– No composting pulled plants

– Weed Wrench/Extractigator

– Remove small seedlings by hand

(waiting until they’re bigger requires tools

for removal)

• HerbicideTriclopyr

– Cut stump

– follow label

instructions for

rates

- - ground level - -

Herb RobertGeranium robertianum

Class B

• aka “Stinky Bob”

• Looks like an innocent

wildflower

• Pink flowers

• Musky odor

• Produces prolific amounts of

exploding seed

• Allelopathic

Dovesfoot Shiny

Shiny GeraniumGeranium lucidum

Class B-Designate/Prohibited Plant List

• Looks like dovesfoot geranium,

a common garden weed

• Shiny leaf

• Pink flower

• Unusual ridged seed pod

Shiny Dovesfoot Stinky Bob

Garlic MustardAlliaria petiolata

Class A/Prohibited Plant List

• displaces understory plants

• smells like garlic and mustard

• allelopathic

• looks like native fringe cup

and/or nettles before it bolts

• Found in most Western WA

counties

• Stinky Bob– Hand pulling before flowering

– Glyphosate spot spraying at 2% in

spring

• Shiny geranium– Hand pulling before flowering

– Glyphosate and Imazapyr

recommended but results have been

mixed

• Garlic Mustard– Hand pulling

– must clean off shoes and

equipment before leaving area

– Glyphosate spot spraying at 2% in

spring

Management Options

• Tall woody shrub

• purple to white spike flowers

• prolific seed producer – 3

million/plant

• competes with willow, a larval food

source for native butterflies

• All cultivars of B.davidii banned in

WA (except for sterile cultivars)

Butterfly bushBuddleja davidii

Class B/Prohibited Plant ListManagement Options

• Hand pull seedlings• recognize early

• Weed Wrench• soil disturbance can sometimes

cause dormant seeds to germinate

• Herbicide–Triclopyr or Glyphosate as a cut

stump treatment

seedling

• Blooming late winter and disappears

by June

• Yellow to white, sometimes orange

flowers

• Reproduces by tubers, bulbils,

bulblets

• Very invasive, streambank erosion,

outcompetes native plants

• Now banned from sale in WA

Lesser CelandineFicaria verna

Class B/Prohibited Plant List

tubersbulbils

2016 Prohibited Plants

Whatcom County - Laurel Baldwin

360-778-6234

Email: LBaldwin@co.whatcom.wa.us

http://www.whatcomcounty.us/914/Weeds

WA ST Noxious Weed Control Board:

http://www.nwcb.wa.gov/

King County Noxious Weed Program:

www.kingcounty.gov/environment/animals

AndPlants/noxious-weeds