Invasive and Noxious Weeds Sasha Shaw King County Noxious Weed Control Program 201 South Jackson, Suite 600 Seattle, WA 98104 206-477-9333 kingcounty.gov/weeds.

Invasive and Noxious Weeds

Sasha ShawKing County Noxious Weed Control Program

201 South Jackson, Suite 600Seattle, WA 98104

206-477-9333kingcounty.gov/weeds

Agenda• Definitions• Impacts• How do weeds

spread?• What can we do to

help stop them?• What are some of

the local invasive weeds?

Weedy Definitions

• Weeds– Plants growing where they are

not wanted• Invasive Weeds

– Non-native plants that spread into natural ecosystems and harm those ecosystems

• Noxious Weeds– Washington State’s legal term for invasive, non-native

plants that threaten agricultural crops, human health, local ecosystems or fish and wildlife habitat

Why do weeds bother people?

• Weeds grow where they want to, not where people plant them

• Weeds take water, food, and space away from the plants we want to grow

• Sometimes weeds can be useful in one place but harmful in another– Like blackberry brambles!

OUCH!YUM!

How are invasive and noxious weeds worse than regular weeds?

• Not just along roads and backyards– Escape into natural areas– Persist and spread– Generally lack predators

and natural controls• Nothing eats it and nothing

out-competes it

• Harm the environment– Bully plants

• They out-grow, out-spread and out-compete native plants

– Disrupt ecosystems

Invasive plants such as English ivy displace native plants and wildlife and can transform entire ecosystems

What are some ways noxious weeds harm ecosystems?

• Decrease biodiversity• Crowd out native plants• Reduce animal habitat and

food sources• Attract pollinators away

from native plants• Clog streams and lakes• Harm trees• Increase erosion• Create fire hazards

Garlic Mustard Infestation

Herb Robert Infestation

Where did our Invasive Weeds come from?

Most invasive weeds in Washington come from parts of the world with similar climates, especially Europe and Asia, because they are most suited to our area.

You are here

How did they get here?

• Intentional (accidentally on purpose)– Ornamental planting– Crops– Erosion control

• Accidental– Ballast material in ships– Contaminated materials

• Seeds• Hay• Live plants

Ornamental escapee Ship ballast and

ornamental escapee

Erosion control Seed and hay contaminant

How do weeds move?

• Natural Processes– Wind– Water/flooding– Birds and other animals

• Human Causes– Hitchhiking on vehicles,

bikes, boots, boats, etc– Construction/Grading– Mowing/Equipment– Yard waste dumping– Being planted

Invasive Weeds Impact Forests

Invasive plants such as English ivy displace native forest plants, damage trees, and replace the foods wildlife are used to eating

Invasive Weeds Impact Lakes

Aquatic weeds create swimming and boating hazards, lower water quality and damage fish habitat

Invasive Weeds Impact Rivers

River banks become covered by invasive knotweed, keeping out native trees and shrubs

The Nature Conservancy

Knotweed increases erosion

Invasive Weeds Impact Agriculture

Pasture weeds crowd out and replace healthy forage* and some weeds can poison animals(*Note: forage means plants that livestock eat)

Cattle checking out a spiny thistle A horse trying not to eat tansy ragwort

http://pss.uvm.edu/vtcrops/articles/PastureWeeds/Pasture_Weeds/Weeds/Cows_avoiding_thistle_sb_uvm.jpg

And Invasive Weeds Are Just Downright Obnoxious

Fighting Invasive Weeds

What does the government do to fight invasive plants and noxious weeds?

• Prevention and early response for new invaders– Watch for new invaders– Require control of certain noxious weeds through state laws

and county weed programs– Prohibit sale of invasive plants and noxious weeds through

quarantine laws• Reducing the impact of widespread invasive plants and

noxious weeds– Hire crews to remove weeds from high quality forests and

replant with native species– Organize volunteer events and train community stewards– Educate people about what not to plant and what to remove

How can we help stop invasive plants?DO

• Learn which plants cause problems

• Watch for and report new plant invaders

• Control weeds on your property• Check clothing, bike, car and boat

for noxious weed “hitchhikers”• Volunteer to remove invasive

plants at stewardship events

DON’T• Don’t plant invasive species• Don’t dump yard waste or

garden clippings in natural areas

• Never dump your aquarium into a lake or stream

http://www.goldcoast.qld.gov.au/environment/aquarium-dumping-10110.html

Some Local Invasive Weeds(also known as “Neighborhood Bullies”)

Himalayan Blackberry(Rubus armeniacus)

Himalayan Blackberry Impacts

• Crowds out other plants

• Reduces habitat diversity

• Creates obstacles to wildlife movement

• Shades out tree seedlings

Controlling Blackberry

• First step, cut canes to the ground– Use long-handled loppers or pruners– Pile up cut stems

• Next step, dig up root balls– Use sturdy shovels and dig deep to get

whole root• Spines are sharp so wear sturdy

clothes– Long pants/sleeves– Sturdy shoes or boots– Leather work gloves

• Remove small patches of blackberry first, then big ones

• Avoid harming native plants

Himalayan Blackberry Identification

Comparing Native and Invasive Blackberry

Native Trailing Blackberry Invasive Himalayan Blackberry

English Ivy (Hedera helix)

Ivy leaves on vines are evergreen, lobed, dull green, with light veins

English Ivy Impacts• Adds weight to the tree;

creates “sail” effect and makes trees more likely to blow down

• Shades out tree’s leaves• Increases rot on tree bark• Smothers understory plants

and tree seedlings• Creates cover for rats near

homesChris Evans, The University of Georgia, www.forestryimages.org

1. Cut vines at about shoulder height and pull them off the trunk below the cut and then keep the area ivy-free.

Use a hand saw or clippers to cut vines and then pull vines off trunk

Ivy Control2. Pull ivy up by the roots and roll it up into a ball.

Start at the top of the hill and work down

Use rakes or potato forks to help yank out roots and gather stems

English Holly (Ilex aquifolium)

Tree or bush with spiny, glossy evergreen leaves and red berries.

English Holly Impacts

• Berries are eaten by birds and deposited in forests, parks and backyards

• Can grow so thickly that native trees and plants can’t grow

• Has invaded remote, natural forests where it has spread undetected for many years

• Expensive and difficult to control, especially in remote areas

English Holly Control

• Young seedlings can be pulled up by hand

• Larger plants have deep roots and have to be dug up with a shovel or large equipment– if you can’t remove all the roots,

cut them below ground• Cutting is only temporary

– Plants sprout from root crowns and stems

– Follow up by removing new shoots for several years to starve out roots

• Can apply herbicide to freshly cut stump or use the hack-and-squirt, girdling or injection methods

http://web.reed.edu/canyon/natu/invasives

Note: Native Oregon Grape can look like English Holly

T.J. Neuffer, WSU Extension

T.J. Neuffer, WSU Extension

Oregon Grape – leaves in pairs, berries blue

English Holly – leaves not in pairs, berries red

K. Messick

Janet Wall

Herb Robert (also called Stinky Bob)(Geranium robertianum)

Herb Robert Impacts• Spreads quickly and

takes over large areas in forested habitats

• Inhibits growth of native forest plants– Produces a chemical

that keeps other seeds from growing

• Seeds are sticky and easily spread by people and animals

• Hitchhikes on hikers into the wilderness where it can spread undetected

Herb Robert Control

Thin, weak roots make this plant easy to pull, but its seeds germinate all season so repeat visits to the same location are needed.

Note: Native Bleeding Heart Looks Like Herb Robert (Stinky Bob)

Native Bleeding Heart Invasive Herb Robert

Image © 2006, G. D. Carr

Image © 2004, Ben Legler

Japanese Knotweed

Knotweed Impacts

• Causes expensive problems– Damages pavement– Limits visibility along roads– Impacts drainage and septic systems– Invades turf and landscapes

• Lowers water quality on rivers by increasing erosion and turbidity

• Forces out native and desirable plants • Reduces habitat for fish and

other wildlife• Prevents tree establishment• One of the most difficult plants to

eradicate• Considered among the worst invasive

plants in Europe and North America

Knotweed spreads easily

• Pieces are spread by floods, mowers, beavers, earth moving equipment, and in contaminated fill material

• Root and stem fragments as little as ½ inch can form new plants

I think I need a bigger shovel.

Knotweed Control

Digging knotweed up is possible but roots may go down 7 feet deep and extend out 20 feet. Re-sprouting is likely.

Knotweed Control Options

Injecting herbicide directly into the hollow stems (very effective but you have to inject every stem).

Covering with thick, plastic fabric for 5 to 7 years to shade it out. Loose covering allows growth without stems breaking through (you have to stomp it down every few weeks).

Spraying plants with an herbicide (use one that won’t harm fish if near a river).

Giant Hogweed (Heracleum mantegazzianum)

Class A Noxious Weed

15 feet tall with a stout, purple-blotched stem, white umbrella-shaped flower clusters, and giant, jagged leaves

Caution: Giant Hogweed Can Cause Burns

Causes blisters followed by purplish-dark blotches that persist and can continue to be sun-sensitive for several years.

Juice causes burns when skin is exposed to sunlight, even a day or two after contact with hogweed. Control must be done very carefully. If juice gets on skin, wash immediately.

Poison Hemlock (Conium maculatum)• Poisonous• 8 to 10 feet tall, stems

purple-spotted• Dig up plants when soil is

moist• Cut flowering stems below

crown before seeds mature– Wear gloves and mow

with a face mask

Poison Hemlock Infestation

Garlic Mustard (Alliaria petiolata)

Class A Noxious Weed

Garlic Mustard

In forests, garlic mustard spreads up to 120 feet in one year. It inhibits tree growth through negative impacts on beneficial fungi and has no natural enemies in North America.

Now spreading on the Cedar River and Coal Creek area, garlic mustard is on the move in King County

Class A Noxious Weed

Garlic Mustard ControlPull it up, bag it up and brush off boots and clothes. Seeds are tiny and spread easily in soil and on boots and clothes.

Class A Noxious Weed

Tansy Ragwort (Senecio jacobaea)Class B Noxious Weed

Tansy Ragwort Infestation in a

Pasture

Toxic alkaloids accumulate in animal’s liver causing irreversible damage and eventually death

Class B Noxious Weed

Tansy Ragwort Control

Pull and bag mature tansy ragwort. Do not leave cut or dried plants on ground (toxic when dry and cut flowers can produce viable seed)

Roots of rosettes need to be removed completely or they will re-sprout.

Class B Noxious Weed

Scotch Broom (Cytisus scoparius)

Scotch Broom Infestation

Scotch Broom can be removed with weed wrenches

Yellow Archangel(Lamiastrum galeobdolon)

Small yellow mint-type flowers in leaf axils Silvery markings on leaves of this popular garden

plant make it easy to spot invading into shady forests

Yellow Archangel taking over the understory of a local forest

Seedlings emerging in treated area

Yellow Archangel Control – Persistence Required!

• Hand pulling – loosen soil and carefully remove all the roots

• Covering – needs to be very well-covered, no holes and extending out from plants

• Spraying – combinations and repeat treatment

• Never leave stems lying on the ground or in piles – they will form roots and grow

• It can take years to get rid of an infestation

Regrowth after spraying

For More Information on Noxious Weeds in King County:

www.kingcounty.gov/weedsWeed Photo Page:

Search by Weed Name

Click thumbnail picture to get more information and photos

Sasha ShawKing County Noxious Weed Control Program

[email protected]

kingcounty.gov/weeds