invasive and noxious weeds sasha shaw king county noxious weed control program 201 south jackson,...
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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
