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

2. Agenda Definitions Impacts How do weeds spread?
What can we do to help stop them?
What are some of the local invasive weeds?

3. Weedy Definitions Weeds Invasive Weeds Noxious 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

4. 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!
Weeds are any plants growing where they are not wanted. Any undesirable grass or broad-leafed plant species, from a small herbaceous plant to a woody shrub, vine, or tree, may be considered a weed if it is growing in a landscape bed, pasture, lawn, rangeland or other area where it is not desired. For example, a corn plant growing in the middle of a lawn would be considered a weed, although easy to control.
OUCH!
YUM!

5. 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
Rapidly multiply to dominate a site and are extremely difficult to control
Introduced to Washington either accidentally or on purpose by humans
Evolved in other parts of the world, lack natural enemies such as plant-eating insects and diseases that normally keep their growth in check in their homeland
Aquatic invasive plants found in Washington were all originally brought here as ornamental plants for aquariums or water gardens. These ornamental plants tend to be naturally hardy and able to withstand the tough growing conditions found in aquariums. Thus, when they are introduced to Washington’s waters, they often thrive and out-compete native plants.
Lack of natural enemies in the US
Heavily planted: of the 124 state noxious weeds, 61 were introduced as ornamentals
Multiple forms of reproduction: many seeds, vegetative growth, fragments
Rapid growth
Easily transported: burs, winged seeds
Invasive plants such as English ivy displace native plants and wildlife and can transform entire ecosystems

6. 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
Herb Robert Infestation
Garlic Mustard Infestation

7. Where did our Invasive Weeds come from?
You are here
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.

8. 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
Seed and hay contaminant
Erosion control

9. How do weeds move? Natural Processes Human Causes 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
Seeds can hitch a ride on almost anything
Seeds are tough and can survive being moved around, buried, frozen, carried long distances, even being eaten by animals
Seeds we plant or hay we feed animals sometimes have weed seeds mixed in
Boats move fragments of water weeds from lake to lake
Boots and camping equipment move weeds from one place to another; from city to forest
If a plant can grow well here and its seeds are spread by birds, water, wind or animals, then it can invade and spread

10. Invasive Weeds Impact Forests
The Environmental Impacts of Noxious Weeds to natural areas are extremely significant.
You are possibly familiar with the impact of English choking forested natural areas in the County.
Invasive species push endangered species over the brink
42% of federally listed endangered species are impacted by invasive species
Invasive plants are the second most important impact to wildlife after habitat loss and fragmentation
The Oregon Silverspot Butterfly is no longer found in Washington partly because invasive plants like Scotch Broom crowded out the butterfly's native food sources.
Invasive plants such as English ivy displace native forest plants, damage trees, and replace the foods wildlife are used to eating

11. Invasive Weeds Impact Lakes
Impacts to recreational use of natural areas can also be great, particularly to aquatic natural areas. Here we have fragrant waterlily and Eurasian watermilfoil Choking this aquatic area.
Aquatic noxious weeds create swimming hazards, snag boats, and interfere with fishing and boating.
Natural areas are the reason many of us live in this region
We expect our parks to be more than just green:
We want natural plant and animal communities; wilderness accessible to urban residents
We want to be able to boat on the lakes, to fish, to swim.
When we go hiking and camping, we want to see natural, diverse ecosystems, not blackberry thickets and ivy deserts
Aquatic weeds create swimming and boating hazards, lower water quality and damage fish habitat

12. Invasive Weeds Impact Rivers
The Nature Conservancy
River banks become covered by invasive knotweed, keeping out native trees and shrubs
Knotweed increases erosion

13. Invasive Weeds Impact Agriculture
Cattle checking out a spiny thistle
A horse trying not to eat tansy ragwort
Significant control costs for land managers
Agricultural costs in terms of reduced livestock and crop productivity
US crop losses are $29 billion a year due to non-native weeds (12% of crop yields)
Many important agricultural weeds in Washington State were initially established in the Puget Sound Area
In King County, significant agricultural impacts are caused by Tansy Ragwort and Milk Thistle
Pasture weeds crowd out and replace healthy forage* and some weeds can poison animals
(*Note: forage means plants that livestock eat)

14. And Invasive Weeds Are Just Downright Obnoxious

15. Fighting Invasive Weeds

16. 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

17. How can we help stop invasive plants?DO
DON’T
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 plant invasive species
Don’t dump yard waste or garden clippings in natural areas
Never dump your aquarium into a lake or stream

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

19. Himalayan Blackberry (Rubus armeniacus)
Robust, sprawling shrub with canes to 9 feet tall, feet long
Large thorns on stems, leaves and leaf stalks
Leaves with 5 large, oval, toothed leaflets
White to light pink flowers and large, black berries
The stems, called canes, grow upright at first, then cascade onto surrounding vegetation, forming large mounds or thickets of the blackberry.
The canes can take root at the tip when they hit the ground, further expanding the infestation.
The berries, which ripen between midsummer and autumn, are used as food by birds, humans and other mammals.
Canes start producing berries in their second year.
Himalayan blackberry can be evergreen, depending on the site.

20. Himalayan Blackberry Impacts
Crowds out other plants
Reduces habitat diversity
Creates obstacles to wildlife movement
Shades out tree seedlings

21. 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

22. Himalayan Blackberry Identification

23. Comparing Native and Invasive Blackberry
Native Trailing Blackberry
Invasive Himalayan Blackberry
Low-growing, trailing, often found in wooded areas
Stems are thin, green when young, brown when mature
Densely covered with smallish thorns
Leaves are evergreen, with 3 leaflets, green on top, lighter green underneath
Leaf: Pinnately compound (usually 3 leaflets), alternate, persistent (often barely); leaflets ovate, lobed and doubly serrate, 1 1/2 to 3 inches long, dark green above and paler below. Rachis and petiole armed with slender, easily detached prickles. Flower: Mostly dioecious, mostly imperfect, white to pink, 1 to 2 inches across, narrow petals, borne in clusters.
Fruit: Black aggregate of drupelets about 1/2 inch long, very edible.
Twig/Bark: Slender, round, and green to red, but covered with a white, waxy bloom, armed with slender straight or recurved prickles that detach easily.
Form: A climbing or trailing evergreen shrub with round, slender branches that commonly reach 10 to 20 feet in length. Young stems are erect, but arch as they lengthen, rapidly touching the ground and rooting at the nodes.

24. English Ivy (Hedera helix)
Ivy leaves on vines are evergreen, lobed, dull green, with light veins

25. 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 homes
Chris Evans, The University of Georgia,

26. Ivy Control
1. Cut vines at about shoulder height and pull them off the trunk below the cut and then keep the area ivy-free.
2. 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
Use a hand saw or clippers to cut vines and then pull vines off trunk
Wear gloves and protective clothing since the sap can cause a reaction in some people
Remove flowers or seed heads you can reach
Hand pull or dig out accessible plants
Clippings need to be removed from the site (can re-root)
Mulching- apply an 8” thick mulch layer. The plants can be cut or removed and then mulched, or a mulch layer can be applied directly on top of the plants.
Mowing can be effective if done very regularly ( weekly)

27. English Holly (Ilex aquifolium)
Tree or bush with spiny, glossy evergreen leaves and red berries.

28. 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

29. 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
English holly control is challenging because you are generally dealing with large trees. Even the small holly plants have extensive, tough roots. The first thing to do is prevent further spread by removing berry-producing trees. Holly trees re-sprout from cut stumps and root crowns so grubbing out the roots is the best non-chemical method. Simply cutting it down will result in years of re-sprouting or multi-stem monsters. Probably the most effective control method is to apply herbicide to a freshly cut stump or use the hack-and-squirt or girdling method (which involves hacking at an angle into the trunk with a small hatchet at regular intervals or completely circling the trunk. The herbicide is then applied into the fresh cuts so it will be translocated down into the roots through the live wood (the cambium). Either glyphosate or triclopyr can be used (see the label for the concentration to use for each). Stem injection of herbicide capsules is another method that shows promise, as well as basal applications for smaller stemmed trees.
In this picture, you can see how dense the holly has become in this forest. The area in the foreground had been filled just as densely with holly before it was manually grubbed out the year before. Notice the lack of any shrubs or young trees in the area where the holly was removed. Surrounding parts of this same forest that were less infested with holly had a much more developed tall shrub layer with a mix of young trees in the understory.

30. Note: Native Oregon Grape can look like English Holly
Oregon Grape – leaves in pairs, berries blue
English Holly – leaves not in pairs, berries red
T.J. Neuffer, WSU Extension
K. Messick
T.J. Neuffer, WSU Extension
When looking for young holly volunteers, be careful to distinguish it from the native look-alike, Oregon grape. The leaves look very similar and without the blue Oregon grape berries or yellow flowers, it might be easy to confuse it with young holly plants. One key difference is that holly leaves grow alternately on the stems (there is only one leaf attached at each node). Oregon grape leaves are in groups of leaflets that are arranged in pairs (except for the one at the end).
Janet Wall

31. Herb Robert (also called Stinky Bob) (Geranium robertianum)
Annual plant with distinctive unpleasant smell
5 petaled flowers that bloom from early spring to late fall
Shade tolerant and can displace native wildflowers
Low growing annual
Geranium family
Pink flowers throughout growing season
Distinct odor when crushed
Stems red in sunny areas
Control
Pull plants before they produce seed capsules

32. 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

33. Herb Robert Control
Annual plant with distinctive unpleasant smell
5 petaled flowers that bloom from early spring to late fall
Shade tolerant and can displace native wildflowers
Low growing annual
Geranium family
Pink flowers throughout growing season
Distinct odor when crushed
Stems red in sunny areas
Control
Pull plants before they produce seed capsules
Thin, weak roots make this plant easy to pull, but its seeds germinate all season so repeat visits to the same location are needed.

34. Note: Native Bleeding Heart Looks Like Herb Robert (Stinky Bob)
Invasive Herb Robert
Image © 2004, Ben Legler
Image © 2006, G. D. Carr

35. Japanese Knotweed

36. 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

37. 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
Starts growth in April, full height by June (10-15 ft)
Rhizomes spread 20 feet or more from parent and go as deep as 7 feet
Root and stem fragments as little as ½ inch can form new plants
Seasonal floods move and break up plants and rhizomes, allowing them to colonize exposed gravel bars and streamsides
Perennial - spreads mainly by fragments
Sections 5 cm or longer produce shoots
Extensive rhizomatous mats - 5 meters deep
Also spreads in contaminated fill
Outgrows and shades out natives and other plants

38. I think I need a bigger shovel.
Knotweed Control
I think I need a bigger shovel.
For new or small patches, you can dig up individual plants if they are growing in soft soil. However, big, established plants like this are very hard to dig up, with large, woody rhizomes and deep roots that are very difficult to dig up. Also, since even a small root fragment can re-sprout, expect to see re-growth around where you dig. Careful work will improve success, but you may make the problem worse if too many roots are left behind. Disturbed roots tend to respond with rapid growth of many stems, often extending out away from where you were digging and into new areas. Make sure to dispose of roots and rhizomes in the garbage, since they can survive most composting attempts and they don’t burn well.
Digging knotweed up is possible but roots may go down 7 feet deep and extend out 20 feet. Re-sprouting is likely. 38

39. Knotweed Control Options
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).
Injecting herbicide directly into the hollow stems (very effective but you have to inject every stem).
Injection: 3ml dose per cane of Glypro (aquatic formulation of Glyphosate). Findings show 5 % regrowth in subsequent years. In 2005, spent 15 days of crew time injecting on the Green River and Soos Creek (hatchery Park).
Spraying plants with an herbicide (use one that won’t harm fish if near a river).

40. Giant Hogweed (Heracleum mantegazzianum)
Class A Noxious Weed
Giant Hogweed (Heracleum mantegazzianum)
Perennial ft tall
Flowers - many small
white flowers in a flat
topped umbel
Stems – thick, ridged, coarse hairs, purple blotches
Introduced as a garden ornamental; Class A noxious weed
Establishes in shaded riparian areas,
including parks and natural areas.
15 feet tall with a stout, purple-blotched stem, white umbrella-shaped flower clusters, and giant, jagged leaves

41. Caution: Giant Hogweed Can Cause Burns
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.
Causes blisters followed by purplish-dark blotches that persist and can continue to be sun-sensitive for several years.

42. 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
Parsnip family (Apiaceae)
6 to 8 feet tall
Tiny white flowers in umbels
Distinctive purple splotches on hollow stems (mature plants)
Leaves are fern like and have a musty odor
Has a large white fleshy tap root
Seeds are paired, 1/8 inch long, brown, ribbed and concave
Reproduces only by seed
Entire plant is toxic
This weed is often mistaken for carrots or parsley because of its fern-like seedling.
All plant parts are poisonous, but fortunately livestock seldom eat the weed unless other feed is not available. Sheep may be poisoned by as little as 4 ounces to 8 ounces of green leaves. Cattle that eat 10 ounces to 16 ounces may be affected. Smaller amounts may cause “crooked calves.”
Use gloves when handling.
Controls
Manual: Control by digging young plants and pulling mature plants before they go to seed.
Biocontrol: hemlock moth (defoliates)
Mechanical: mow prior to seed production; hand pull while wearing gloves
Chemical: MCPA or 2,4-D (if allowed on your site) at seedling to rosette stage; glyphosate before bolt; metsulfuron on growing plants; don’t graze in area for 3 weeks after spraying

43. Poison Hemlock Infestation

44. Garlic Mustard (Alliaria petiolata)
Class A Noxious Weed
Garlic Mustard (Alliaria petiolata)

45. Garlic Mustard Class A Noxious Weed
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

46. Garlic Mustard Control
Class A Noxious Weed
Garlic Mustard Control
Pull it up, bag it up and brush off boots and clothes. Seeds are tiny and spread easily in soil and on boots and clothes.

47. Tansy Ragwort (Senecio jacobaea)
Class B Noxious Weed
Tansy Ragwort (Senecio jacobaea)
A biennial plant; rosettes the first year and in the spring; flowering stems the following year and in the summer
Controls
Manual: Hand pull or dig up small infestations.
Biocontrols: Cinnabar moth, ragwort flea beetle
Mechanical: Mowing is not recommended.
Herbicide: Most effective to apply selective broadleaf herbicides in the spring and again in the fall. Glyphosate; 2,4-D on rosettes; metsulfuron and dicamba on growing plants. 47

48. Tansy Ragwort Infestation in a Pasture
Class B Noxious Weed
Tansy Ragwort Infestation in a Pasture
A biennial plant; rosettes the first year and in the spring; flowering stems the following year and in the summer
Controls
Manual: Hand pull or dig up small infestations.
Biocontrols: Cinnabar moth, ragwort flea beetle
Mechanical: Mowing is not recommended.
Herbicide: Most effective to apply selective broadleaf herbicides in the spring and again in the fall. Glyphosate; 2,4-D on rosettes; metsulfuron and dicamba on growing plants.
Toxic alkaloids accumulate in animal’s liver causing irreversible damage and eventually death

49. Tansy Ragwort Control Class B Noxious Weed
Controls
Manual: Hand pull or dig up small infestations.
Biocontrols: Cinnabar moth, ragwort flea beetle
Mechanical: Mowing is not recommended.
Herbicide: Most effective to apply selective broadleaf herbicides in the spring and again in the fall. Glyphosate; 2,4-D on rosettes; metsulfuron and dicamba on growing plants.
Roots of rosettes need to be removed completely or they will re-sprout.
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)

50. Scotch Broom (Cytisus scoparius)
Evergreen shrub with green, ridged stems
Flowers bright yellow and pea-shaped
Leaves small, oval, in threes or single
Flat seedpods with hairs on edges only, 1-2 inches long
From Europe, planted in gardens and for erosion control; introduced around the 1860’s
Seeds remain viable up to 80 years
Seeds emerge best when close to the surface (<1 inch); don’t usually germinate when buried over 4 inches, unless soil is disturbed
Small nodules on the roots harbor beneficial, N-fixing bacteria that allow broom to thrive even in poor soils
Plants began to degrade after 6 to 8 years and die by 10 to 15 years; older plants have a mix of dead, woody material and green growing parts (fire fuel)

51. Scotch Broom Infestation

52. Scotch Broom can be removed with weed wrenches
Keep soil disturbance to a minimum where possible
At least ten years or more of monitoring site for new seedlings
If you don’t plan to maintain, don’t bother clearing – will be covered again within 5 years
Plants under 3 feet can be hand pulled when soil is moist
Larger plants can be removed with weed wrenches, claw mattocks, root jacks or other useful tools; do this when the soil is moist
Clear thick stands or multi-branched plants with manually operated tools: chainsaws, brush cutters, axes, machetes, loppers
Cut plants near ground level where the stem is more yellow than green in the dry season (July-September)
Cut large, mature plants at chest height or below and cut off side branches during the dry season
Key to success is to keep seeds from forming after initial clearing
After using tractor-mowers or other tools, usually need to follow-up with more cutting or herbicides; wait until leaves have fully developed on re-sprouted stems before treating with herbicides
Foliar herbicide application is most effective after full leaf development and before fall senescence
For less dense sites, use selective treatment – cut stump (late spring), stem injection, basal/stem spray (in fall)

53. Yellow Archangel (Lamiastrum galeobdolon)
Currently on the State Monitor list
King County made a case for listing but not approved as a state noxious weed
Escaping into urban and rural forests
Potential for being a huge problem in shady forests
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

54. Yellow Archangel taking over the understory of a local forest

55. 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
Seedlings emerging in treated area

56. For More Information on Noxious Weeds in King County:
Weed Photo Page:
Search by Weed Name
Click thumbnail picture to get more information and photos

57. Sasha Shaw King County Noxious Weed Control Program 206-477-9333 sasha
Sasha Shaw King County Noxious Weed Control Program kingcounty.gov/weeds