Backyard Invasions: Noxious Weeds in Seattle's Greenspaces Sasha Shaw King County Noxious Weed Program

Agenda  Definitions  Impacts of Invasives in Urban Areas  Invasive Vines, Trees, Shrubs and Other Plants  What Can We Do?  Resources

What is a Weed?  a plant out of place  takes water, nutrients or habitat from desired plants (subjective)  threatens an area’s values or benefits

Are All Weeds Bad All the Time?  Lots of weedy plants are used by birds, insects and people  One person’s weed can be another person’s pride and joy  Native plants used to be called weeds and still are for some! American goldfinch lunches on bull thistle seeds

What are Native Plants?  Adapted to local climate and soils; foundation for local ecosystem  Co-evolved with native animals  Provide food, shelter, nesting materials for wildlife Gumweed (Grindelia integrifolia) on Puget Sound beach, native to Pacific coast from BC to California

What is an Invasive Weed?  Non-native, aggressively spreading Destructive Destructive Competitive Competitive Difficult to control Difficult to control Invasive knotweed spreading into an open forest

Good Plant Bad Weed Bleeding Heart (Dicentra formosa) Herb Robert (Geranium robertianum)  Some invasive weeds resemble native plants  Invasive weeds exploit conditions similar to their home range and don’t have natural enemies keeping them in check

What is a Noxious Weed?  Non-native plant that impacts agriculture, wildlife, human health, land values or natural resources  Defined and regulated by state law (RCW 17.10) control required only where weed is not widespread control required only where weed is not widespread goal of law is to prevent spread of new invaders to un-infested areas goal of law is to prevent spread of new invaders to un-infested areas

What are the Weed Classes?  Class A Weeds – new invaders, control required statewide, still a chance to eradicate  Class B and C Designates – control required in King County, still have a chance to stop them from getting established  Non-Designates and Weeds of Concern – widespread invasive weeds in King County, control not required but definitely a good idea whenever possible!

How do weeds get here?

Orange Hawkweed: from garden store to mountain meadow Noxious Weeds Run Amok:

Impacts of Invasive Weeds

EnvironmentalImpacts Invasives like English Ivy transform forests and natural areas, hurting trees, native plants and native wildlife species

Purple and garden loosestrife in Portage Bay choke out native plants and destroy wildlife habitat. Diverse wetland habitat in the Nisqually delta provides food and shelter for many different kinds of birds and animals.

Impacts to Waterways Restoration crew removes reed canary grass that had filled in a stream channel, increasing flooding and reducing fish habitat

Impacts to Recreation Fragrant water lily and Eurasian watermilfoil in Lake Sammamish

Impacts to Public Health Giant Hogweed - Sap sensitizes skin to UV radiation, resulting in severe burns, blisters, painful dermatitis and scarring.

Impacts of Invasives in Seattle Dan DeLong/Seattle Post-Intelligencer

Seattle Urban Nature Project  City-wide Surveys and ,000 acres of public lands in Seattle 8,000 acres of public lands in Seattle Classified habitat types throughout the city Classified habitat types throughout the city Recorded species names and percent cover Recorded species names and percent cover Study of all forest types in Seattle Study of all forest types in Seattle Mapped density of invasives Mapped density of invasives Ella Elman & Nelson Salisbury, Ecologists (206)

Invasive Plant Species Citywide 11% 25% 17% 18% 20% 9% In 47% of Seattle’s forests, the majority of the plant cover consists of invasive species

Most Prevalent Invasive Species

Invasive Trees: An Overlooked Threat  Seattle has 2500 acres of forested parkland  60-70% of tree regeneration in Seattle’s forests is non-native  Shade tolerant species are the biggest threat: English holly and cherry laurel are the worst  European species of mountain-ash, hawthorne, and cherry are found throughout Seattle’s forests  If nothing is done, 30 to 40 years from now our forests will look dramatically different than they do today

Tree Regeneration Conifer/deciduous ForestsConifer/madrone Forests

Case Study: Deadhorse Canyon Inventory  Distribution of English holly and cherry laurel Red and orange high density Yellow moderate Green low

Invasive Trees: Evergreen English holly Cherry laurel Portugal laurel

English Holly (Ilex aquifolium)  Tree 15 to 50 feet tall and 15 feet wide  Bark smooth and gray  Leaves glossy, persistent, dark green, wavy and spiny  Flowers are small and white  Berries are bright red or orange and found in small bundles like the flowers

English Holly (Ilex aquifolium)  can form thickets of large, densely packed trees in shady forests or open areas  spreads by seeds eaten by birds; can establish in remote areas  re-sprouts indefinitely from cut stumps so digging is best non- chemical method

Holly Look Alike: Tall Oregon Grape

English Laurel or Cherry Laurel (Prunus laurocerasus)  Evergreen tree or shrub to 20 feet high  Leaves leathery, glossy, 3 to 7 inches, slightly toothed  Flowers white, fragrant, in elongated clusters  Native to Eastern Europe, Asia Minor  Common landscaping hedge

English Laurel (Prunus laurocerasus)  Fast-growing 25 inches or more per year  Fruit fleshy, black with a large pit (stone)  Widely escaped in local natural areas and woodlands  Highly toxic if ingested poisonous parts: wilted leaves, twigs (stems), seeds

Invasive Trees: Deciduous European Mountain-ash English Hawthorne Sweet Cherry Norway Maple

English Hawthorne (Crataegus monogyna)

European Mountain-ash (Sorbus aucuparia)

European Sweet Cherry (Prunus avium)  A small to medium sized tree, generally to 50 feet, with a broadly rounded crown  Leaf 2 to 5 inches long with serrated margin  Flowers showy, white, one inch across  Cherries sweet, dark red to nearly black, 1/2 to 1 inch across

Norway Maple (Acer platanoides)  Common shade tree  Escaping into Seattle forests  Similar to native bigleaf maple, but the leaf is not as large or deeply cut  Seeds spread their wings wider and have no bristly hairs

Invasive vines  Form dense groundcovers excluding all native plants  Climb up and smother trees  Add weight to tree canopies  Form dense groundcovers excluding all native plants  Climb up and smother trees  Add weight to tree canopies English ivy Old man’s beard

English or Atlantic Ivy (Hedera hibernica, H. helix) Ivy leaves are evergreen, lobed, dull green, with light veins Ivy leaves are evergreen, lobed, dull green, with light veins Class C Noxious Weed – Control Not Required

English or Atlantic Ivy (Hedera hibernica, H. helix) mature ivy leaves are shiny green and not lobed mature ivy leaves are shiny green and not lobed umbrella-like clusters of greenish-white flowers in the fall umbrella-like clusters of greenish-white flowers in the fall black, berry-like fruit in winter, seeds mature in spring black, berry-like fruit in winter, seeds mature in spring Class C Noxious Weed – Control Not Required

Ivy mats smother understory plants and tree seedlings - changing the natural succession patterns of forests. Ivy climbs trees, weighs down branches, shades leaves, damages bark English Ivy Class C Noxious Weed – Control Not Required

Old Man’s Beard (Clematis vitalba) Class C Noxious Weed – Control Not Required

Old Man’s Beard or Wild Clematis Old Man’s Beard covering trees at Magnuson Park Old Man’s Beard on trees in Ravenna Park Class C Noxious Weed – Control Not Required

Invasive Shrubs  Form dense thickets excluding all native plants  Establish in disturbed sites  Spread by birds, wind and people  Form dense thickets excluding all native plants  Establish in disturbed sites  Spread by birds, wind and people Scotch broomHimalayan blackberry

Himalayan Blackberry ( Rubus armeniacus or Rubus discolor )

Evergreen Blackberry (Rubus laciniatus)

Himalayan Blackberry (Rubus discolor)

Good Guy Look Alike: Native Trailing Blackberry (Rubus ursinus)

Scotch Broom (Cytisus scoparius) Class C Noxious Weed – Control Not Required

Scotch broom removal with weed wrenches Controlling Scotch broom with weed wrenches at Marymoor Park Class C Noxious Weed – Control Not Required

Cotoneaster Shrubs  Thornless shrub up to 15" tall with arching branches  Small leaves white-hairy underneath  Little white flowers and dull red fruits  Colorful fruits attractive to birds leading to easy spread and invasiveness  Increasingly common in Seattle’s forests

Invasive Perennials and Groundcovers  Fast-growing invasives push out native wildflowers and groundcover species  Tall perennials out-compete even shrubs and small trees especially on streams  Often escapees from gardens or spreading from yard waste dumps

Giant Hogweed (Heracleum mantegazzianum) Class A Noxious Weed

Giant Hogweed (Heracleum mantegazzianum) Hogweed scars remain sensitive to sunlight for several years Hogweed burns are often painful and slow to recover Cutting the large, fleshy stems may spray sap on exposed skin Class A Noxious Weed

Hogweed leaves are large and deeply dissected, stems are hairy with purple blotches Giant Hogweed (Heracleum mantegazzianum) Class A Noxious Weed

Garlic Mustard (Alliaria petiolata) Class A Noxious Weed

Garlic Mustard (Alliaria petiolata) Dense infestation along Longfellow Creek Growing on a stump in the forests of Golden Gardens Park Class A Noxious Weed

Garlic Mustard (Alliaria petiolata)

Policeman’s Helmet (Impatiens glandulifera) Annual with fleshy, reddish stems, 3-10 ft tall, flowers resemble English policeman’s helmet, vary in color from white to dark pink-purple Class B Noxious Weed

Policeman’s Helmet (Impatiens glandulifera) Can grow to 10 feet tall in one season Class B Noxious Weed Policeman’s helmet spreads along creeks and out-competes and crowds out other plants

Policeman’s Helmet (Impatiens glandulifera) Class B Noxious Weed

Policeman’s Helmet (Impatiens glandulifera) Class B Noxious Weed

Knotweeds (Polygonum spp.) Class B Noxious Weed – Control Not Required

Typical stand of Bohemian knotweed with stiffly upright male flower clusters Class B Noxious Weed – Control Not Required

Knotweed rapidly spreads along rivers as fragments get moved by floods and grow into new clones downriver Knotweed Invasion on Rivers Class B Noxious Weed – Control Not Required

Despite knotweed’s large rhizome mass, it provides poor erosion control

Herb Robert (a.k.a. Stinky Bob) Class C Noxious Weed – Control Not Required

Herb Robert (a.k.a. Stinky Bob) (Geranium robertianum) Shallow roots make this plant easy to pull but seeds germinate all season so repeat visits to the same location are needed. Class C Noxious Weed – Control Not Required

Yellow Archangel Lamiastrum galeobdolon (a.k.a. Lamium) Small yellow mint-type flowers in leaf axils Slivery markings on leaves of this popular garden plant make it easy to spot invading into shady forests Proposed Class C Noxious Weed – Control Not Required

Yellow Archangel (Lamiastrum galeobdolon) Yellow archangel spread aggressively into this Kirkland-area forest Proposed Class C Noxious Weed – Control Not Required

Poison Hemlock (Conium maculatum) Class C Noxious Weed – Control Not Required

Poison Hemlock (Conium maculatum) Class C Noxious Weed – Control Not Required

Aquatic Weeds  Choke out native water plants  Reduce fish and wildlife habitat value of streams and lakes  Endanger swimmers and boaters  Highly costly to manage once established and almost impossible to eradicate

Eurasian Watermilfoil (Myriophyllum spicatum) Class C Noxious Weed – Control Not Required

Eurasian Watermilfoil (Myriophyllum spicatum) Class C Noxious Weed – Control Not Required

Fragrant Waterlily (Nymphaea odorata) Infestation on Cottage Lake Showy flower and notched leaves Class C Noxious Weed – Control Not Required

Purple Loosestrife (Lythrum salicaria) Class B Noxious Weed

Purple Loosestrife (Lythrum salicaria) Class B Noxious Weed

Garden Loosestrife (Lysimachia vulgaris) Yellow, primrose-like flowers clustered near top of the plant Sepals have distinct orange margins Class B Noxious Weed

Garden Loosestrife (Lysimachia vulgaris) Class B Noxious Weed

Common Reed (Phragmites australis) Large perennial grassLarge perennial grass Freshwater or brackish waterFreshwater or brackish water Can grow to 12 feet tallCan grow to 12 feet tall Leaf sheath looseLeaf sheath loose Reproduction mostly by rhizomesReproduction mostly by rhizomes Tall feathery flower head Class C Noxious Weed – County-select

Common Reed (Phragmites australis) Creeping rhizomes and stolons help this plant spread along waterways and form large clones Class C Noxious Weed – County-select

Eek! What Can We Do?

First, Start at Home  Learn to recognize & eliminate noxious weeds before they establish  Choose non-invasive species for landscapes & gardens  Control seed production at a minimum  Replant with appropriate species  Dispose of noxious weeds properly  Check vehicles, clothing and equipment

Control Methods for Noxious Weeds Management Manual Mechanical Chemical Biological Control Chart by Minnesota Sea-Grant

Pull seedlings and young plants when small, before root systems fully developPull seedlings and young plants when small, before root systems fully develop Remove as much of the root as possibleRemove as much of the root as possible Limit disturbance and be sure to follow-upLimit disturbance and be sure to follow-up Pulling and bagging tansy ragwort Digging purple loosestrife Manual control of Scotch broom Manual Control

Useful to reduce size, seed production and to starve roots, especially when plants cover large areasUseful to reduce size, seed production and to starve roots, especially when plants cover large areas Weeds will resprout after mowing and can be spread on equipment if not carefulWeeds will resprout after mowing and can be spread on equipment if not careful Best results when combined with manual controlBest results when combined with manual control Himalayan Blackberry can be mowed to remove brambles Mechanical Control

 Safety: Use with caution, protect skin and eyesUse with caution, protect skin and eyes Always follow the directions on the labelAlways follow the directions on the label Prevent drift into water, other plants, etcPrevent drift into water, other plants, etc  Applications: Spot treatments, target the weed and avoid injury to desirable plantsSpot treatments, target the weed and avoid injury to desirable plants Incorporate other treatment methodsIncorporate other treatment methods Choose the least harmful herbicide that is appropriate for the weed and the siteChoose the least harmful herbicide that is appropriate for the weed and the site Chemical Control

 Mulching Suppresses weeds & improves soil Suppresses weeds & improves soil  Techniques Bark, compost, newspaper, cardboard Bark, compost, newspaper, cardboard Geotextile fabric Geotextile fabric Plastic Plastic Sheet Mulching

Finally, Disposal and Follow up  Disposal Remove flowers & seeds – bag and send to landfill or burn Remove flowers & seeds – bag and send to landfill or burn Composting – use for common invasives, not for noxious weeds Composting – use for common invasives, not for noxious weeds On-site composting vs. clean green yard waste On-site composting vs. clean green yard waste  Monitor The second and third year are crucial for effective weed control The second and third year are crucial for effective weed control

Next Step, Become a Weed Warrior  Watch for new plant invaders  Volunteer at invasive removal work parties and stewardship events  Organize your friends, co-workers, and neighbors to “adopt” a park or natural area  Spread the word on neighborhood bullies!

Local Contacts for Volunteering  King County Parks and Open Space Volunteer Coordinator: Tina Miller, Volunteer Coordinator: Tina Miller, Calendar: Calendar:  Watershed Stewardship Directory groups and agencies helping to preserve and restore King County's watersheds groups and agencies helping to preserve and restore King County's watersheds  Seattle Urban Forests Contact: Peter Noonan, (206) Contact: Peter Noonan, (206)  Seattle Parks  Seattle Creeks Contact: Bob Spencer, (206) Contact: Bob Spencer, (206)

Sign up for newsletter at: It is a free, quarterly publication sent out by only. Each issue features information about SUN research in Seattle’s forests and our current community projects. Seattle Urban Nature Newsletter

King County Noxious Weed Program  6 year-round staff and 8 seasonal weed specialists  Goal is to prevent and reduce the economic, environmental and social impacts of noxious weeds  Weed surveys, education and outreach, landowner contact, site specific control options

King County Noxious Weed Program Staff  Program Manager: Steve Burke  Education Coordinator: Sasha Shaw  Admin Specialist: Suzanne Rowe  State Lands Coordinator: Sean MacDougall  County Lands Coordinator: Roy Brunskill  Aquatic Weed Specialist: Katie Messick  Seasonal Weed Specialists: Amy Yahnke, Dennis Chambreau, Trish MacLaren, Sarah Baker, Monica Walker, Karen Peterson, Maria Winkler, Frances Lucero Amy Yahnke, Dennis Chambreau, Trish MacLaren, Sarah Baker, Monica Walker, Karen Peterson, Maria Winkler, Frances Lucero  Contact us at or

King County Noxious Weed Control Program Website Weed Photo Page: Search by Common Name or Latin Name Click thumbnail picture of plant

Sasha Shaw King County Noxious Weed Program 201 South Jackson St, Suite 600 Seattle, WA