Invasive Weeds Sasha Shaw King County Noxious Weed Control Program 201 South Jackson, Suite 600 Seattle, WA 98104 206206-296296-0290 http://www.kingcounty.gov /weeds http://www.kingcounty.gov/weeds

Agenda ¾ Definitions ¾ Impacts of Invasive Plants ¾ Weed Control Strategies ¾ Invasive Weeds in Natural Areas z z z z

Trees Shrubs and Vines Herbaceous Plants and Groundcovers Regulated Noxious Weeds

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What is an Invasive Weed? ¾ ¾

Introduced / non-native Ability to out-compete native plants z

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Lack of predators or natural controls Ability to modify local ecology Aggressive ability to reproduce

Invasive knotweed is one of the toughest plants to control and damages some of the highest quality habitats

What is a Noxious Weed? ¾ Non-native plant that impacts

agriculture, wildlife, human health, land values or natural resources ¾ Defined and regulated by state law (RCW 17.10) z

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control required only where weed is not widespread goal of law is to prevent spread of new invaders to un-infested areas

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Growing vs. Selling Noxious Weeds ¾ Prohibited Plants List (WAC 16-752) z z

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Goal is to prevent spread of new introductions List is determined by WSDA, enforced by state Nursery Inspection Program Prohibits sale and purchase of plants and seeds

¾ Noxious Weed List (WAC 16-750) z

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Weeds regulated where they are beginning to invade but not yet widespread List set by state weed board; law enforced by county noxious weed boards Requires property owners to prevent plants from seeding

What are the Weed Classes? ¾

Class A Weeds z

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control provides statewide benefits (sometimes even greater)

Class B and C Designates z

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new invaders, control required statewide; still a chance to eradicate

control required in King County, still have a chance to stop them them from getting established control provides regional or countywide benefits

NonNon-Designates and Weeds of Concern z

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widespread invasive weeds in King County, control not required but definitely a good idea whenever possible control provides local or sitesite-specific benefits; more if efforts are coordinated with neighbors

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King County Noxious Weed Program ¾

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6 yearyear-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 206206-296296-0290 control options [email protected]

Impacts of Invasive Weeds

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Impacts on Resources

Natural resources, recreation and agriculture are all impacted by by invasive weeds

Impacts on Native Habitats and Species

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

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Invasive Plants in Urban Forests Percent Percent cover cover of of invasive invasive species species present present in in Seattle's Seattle's urban urban forests forests

Trace Trace (0-10%) (0-10%) Ve Very ry High High (>100%) (>100%) 11% 20%

High High (81-100%) (81-100%)

25%

9%

Low Low (11-30%) (11-30%)

18% 17%

M Mode oderate rately ly High High (51-80%) (51-80%)

M Meedium dium (31-50%) (31-50%)

In 47% of Seattle’s forests, the majority of the plant cover consists of invasive species

Invasive Plants in Urban Forests • 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 mountainmountain-ash, hawthorne, hawthorne, and cherry are found throughout Seattle’ Seattle’s forests

• If nothing is done, 30 to 40 years from now our forests will look dramatically different than they do today • The same trend is beginning to show up in suburban and rural forests

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Most Prevalent Invasive Species Five most invasive species in Seattle based on 1999-2000 survey 1200 1000

Acres

800 600 400 200 0 Himlalayan blackberry (Rubus discolor)

English ivy Scotch broom (Hedera helix) (Cytisus scoparius)

English holly (Ilex aquifolium)

Old man's beard (Clematis vitalba)

Species

Weed Control Strategies

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Ecology-Based Weed Management ¾ ¾

Old approach – see the weed, kill the weed New approach – focus on prevention and establishing invasioninvasion-resistant plant communities z z z

minimize disturbance like tillage, trampling use competition from established vegetation to help hold off weeds weeds different strategies work at different stages of weed invasion Weed Population Growth

Restore

Control Prevent

Time

Decide on Goals and Make a Plan New and small infestations •Prevention of spread is first priority •Eradication is still feasible Established, large infestations •Decide on level of control needed to reduce impact

Clipping purple loosestrife flowers

•Stop seed production to contain spread

Bull thistle infestation

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Weed Life Cycles ¾

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One season from seedling to producing seeds Use cover crops or mulch

Biennial z

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Common Groundsel Seedling

Annual

First year: develop roots and lowlow-growing leaves (rosettes) Second year: flowers, sets seed and matures

Tansy Ragwort

Perennial z z

Live more than two years Often reproduce by vegetative means as well

Spotted Knapweed

Get to Know your Roots

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Prevention: Think about How Weeds Move Around

Manual Control •Pull seedlings and young plants when small, before root systems fully develop •Remove as much of the root as possible •Limit disturbance and be sure to follow-up Digging giant hogweed

Pulling and bagging tansy ragwort

Manual control of Scotch broom

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Mechanical Control •Useful to reduce size, seed production and to starve roots •Weeds will resprout after mowing and can be spread by harrowing and other practices •Best results when combined with manual control

Himalayan Blackberry can be mowed to remove brambles

Chemical Control ¾Safety: •Use with caution, protect skin and eyes •Always follow the directions on the label •Prevent drift into water, other plants, etc

¾Applications: •Spot treatments, target the weed and avoid injury to desirable plants •Incorporate other treatment methods •Choose the least harmful herbicide that is appropriate for the weed and the site

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Cultural Control ¾

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Changes to environment to suppress weeds Shade/Cover z z

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Thick mulch Cardboard plus woodchips Weed fabric

Competition z z

Sterile grass Dense plantings of quick growing shrubs and trees

Finally, Follow up and Dispose Follow Up: • Check site for several years • Mulch to suppress weeds & improve soil • Fill in holes with lowlow-maintenance natives Disposal: • Best: pull before flowering and compost! • Flowers & seeds shouldn’ shouldn’t go in backyard compost • Noxious weeds: discard in garbage • Widespread weeds: city yard waste

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Invasive Weeds in Natural Areas

Invasive Trees: Evergreen

English holly

Portugal laurel Cherry laurel

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English Holly (Ilex aquifolium) ¾ ¾ ¾

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15 to 50 feet tall and 15 feet wide Leaves glossy, persistent, dark green, wavy and spiny Flowers small and white; Berries are bright red or orange in clusters 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 ReRe-sprouts from cut stumps and root crowns so digging is best nonnon-chemical method

Holly Look Alike: Tall Oregon Grape

www.PlantSystematics.org

http://courses.washington.edu/ehuf331/Photos/Berberis_a quifolium_4_kbCo.jpg

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English Laurel or Cherry Laurel (Prunus laurocerasus) ¾ ¾

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Evergreen tree or shrub to 20 ft tall Leaves leathery, glossy, 3 to 7 inches, slightly toothed Flowers white, in elongated clusters and fruit black with large pit Grows fast, 25 inches or more per year Widely escaped in local natural areas and woodlands Highly toxic if ingested z

poisonous parts: wilted leaves, twigs (stems), seeds

Invasive Trees: Deciduous

European Mountain-ash

English Hawthorne

Sweet Cherry

Norway Maple

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Invasive Shrubs and Vines

Cotoneaster Species ¾

Evergreen shrubs 66-13 ft tall with arching branches or lowlow-growing z

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Leaves oval, with dull green upper surface and a white underside with a covering of fine hairs Clusters of small white or pink flowers followed by small red to orangeorange-red fruits

Fruits attractive to birds leading to easy spread and invasiveness Also spread by yard waste dumping Dense infestations will smother native vegetation Increasingly common in Seattle’ Seattle’s forests

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Himalayan Blackberry (Rubus armeniacus or Rubus discolor)

Evergreen Blackberry (Rubus laciniatus)

http://www.nic.funet.fi

http://www.biopix.dk

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

Blackberry Control ¾

Plan work based on ability to maintain and rere-vegetate z z

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Least infested areas first, then more heavily infested areas Preserve native and beneficial vegetation for competition

Clear mature blackberry with loppers, brush mowers, weed eaters, machetes (or goats) before seed set Dig up root crowns or spot spray rere-sprouting canes at about 2 ft tall in late summer or fall (foliar spray or wiped onto fresh cut stems) Can cut several times a year for several years to exhaust the roots Wetlands: cut to ground level in late summer through early winter just before soil flooding occurs Mulch and rere-vegetate as needed to avoid soil erosion and weed problems Plant conifers: dense shade will ultimately reduce blackberry problems

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Scotch Broom (Cytisus scoparius)

Scotch Broom Control ¾ ¾ ¾ ¾

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Keep soil disturbance to a minimum where possible Plan for at least ten years or more of monitoring site for new seedlings Plants under 3 feet can be hand pulled when soil is moist Larger plants can be removed with weed wrenches, wrenches, claw mattocks, root jacks or other useful tools; easiest when the soil is moist For large infestations, cut plants near ground level where the stem is more yellow than green; much more effective when done in the dry season (July(July-September) Key to success is to keep seeds from forming after initial clearing

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Scotch broom removal with weed wrenches

Controlling Scotch broom with weed wrenches at Marymoor Park

English or Atlantic Ivy (Hedera hibernica, H. helix)

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

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English or Atlantic Ivy (Hedera hibernica, H. helix) • mature ivy leaves are shiny green and not lobed • umbrellaumbrella-like clusters of greenishgreenish-white flowers in the fall • black, berryberry-like fruit in winter, seeds mature in spring

English Ivy Control Kill upper growth by cutting the vines all around the tree at about shoulder height and prying them off the base of the tree. Then work on pulling the ivy growing on the ground.

Cut stems and pull off trunks

Ivy vines have died after being cut and removed from base of tree; leaves will stay green for at least a year

Kiwanis volunteers pulling ivy alongside a creek on Bainbridge Island

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English Ivy Control

Old Man’s Beard (Clematis vitalba)

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Old Man’s Beard or Wild Clematis

Old Man’s Beard on trees in Ravenna Park Old Man’s Beard covering trees at Magnuson Park

Invasive Herbaceous Plants and Groundcovers ¾ ¾ ¾

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

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Invasive Knotweeds (Polygonum cuspidatum et al)

Hollow, upright, bamboo like stems often reddish or red-speckled

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Knotweed Invasion on Rivers ¾

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Considered one of the worst invasive plants in riparian habitats Difficult to control especially in sensitive areas Control from top of watershed down Covering or chemical treatment work if done well

Knotweed rapidly spreads along rivers as fragments get moved by floods and grow into new clones downriver

Reed Canarygrass (Phalaris arundinacea)

Forms dense stands, excluding other plants and filling in small waterways, blocking fish passage and increasing flooding

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Reed Canarygrass Identification ¾ ¾ ¾

¾ ¾ http://popgen.unimaas.nl/~ jlindsey/commanster

http://popgen.unimaas.nl/~jlindsey/comman ster/Plants/Grasses

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Flowers JuneJune-July 3 to 6 feet tall, varies based on habitat Sturdy, hollow stems up to ½ inch diameter, some reddish color near top Leaf blades are flat, hairless, ¼ to ¾ inch wide Flowers on 3 to 7 inch long clusters high above leaves Flowers clusters are branched and compressed into a spikespiketype shape Long ligule is helpful character Leaves come off stem at 45 degree angle Reddish colored rhizome

Reed Canarygrass Control ¾ ¾ ¾

HandHand-pulling/digging 22-3 times per year for five years over whole population Cutting at least 5 times a season Cover with landscape fabric or plastic z

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Best results with thick woven plastic fabric (e.g. Mirafi or Amoco brands); for at least one year

Shade out with dense plantings of willows or other thicket forming shrubs Glyphosate 2% plus surfactant in midmidsummer (just prior to summertime dormancy) or preferably in late fall (before frost dieback) Seed with desirable plants to avoid erosion or rere-invasion by weeds Combine a variety of methods for best results

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Field and Hedge Bindweed (Convolvulis arvensis and Calystegia sepium)

Field Bindweed ¾ ¾ ¾

Hedge Bindweed

Emerges: February to April Flowers: May to August Seeds: September to October

Hedge Bindweed (Calystegia sepium)

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Bindweed Control ¾

Frequent hand-pulling will eventually control plants z

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Need to pull up as much root as possible Take care not to leave root fragments behind, they make more plants!!

Covering plants with geotextile fabric/black plastic – at least 3 years of complete coverage Early detection/rapid response is crucial after clearing areas of blackberries and other invasives

Bittersweet Nightshade (Solanum dulcamara)

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Herb Robert (a.k.a. Stinky Bob)

Herb Robert Control: Pull and Pull Some More

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

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Yellow Archangel Lamiastrum galeobdolon (a.k.a. Lamium)

Small yellow mintmint-type flowers in leaf axils

Slivery markings on leaves of this popular garden plant make it easy to spot invading into shady forests

Yellow Archangel: Big Finn Hill Park

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A Few Regulated Noxious Weeds ¾ Prevention of spread in the county and

state is highest priority ¾ Call the Noxious Weed Program if you find these (or other regulated) noxious weeds: 206-296-0290

Class A Noxious Weed

Giant Hogweed (Heracleum mantegazzianum)

15 feet tall with a stout, purple-blotched stem, large white umbrellashaped flower clusters, and giant, sharply toothed leaves

ashtabula.osu.edu

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Class A Noxious Weed

Giant Hogweed – Use Caution When Handling

Sap from hogweed causes painful burns Wear gloves and long sleeves when cutting off flower heads, then dig up roots

Class A Noxious Weed

Garlic Mustard (Alliaria petiolata)

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Garlic Mustard (Alliaria petiolata)

Class A Noxious Weed

Infestation along Longfellow Creek

Class A Noxious Weed

Garlic Mustard (Alliaria petiolata)

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Class B Noxious Weed

Purple Loosestrife (Lythrum salicaria) ¾ ¾ ¾ ¾ ¾

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Escaped from gardens nationwide OutOut-competes native plants Up to 2.5 million tiny seeds per plant Chokes out fish and wildlife habitat 500,000 acres affected in North America each year Leaves opposite, stems square, flowers in narrow spikes in July and August

Garden Loosestrife (Lysimachia vulgaris)

Class B Noxious Weed

Sepals have distinct orange margins

Yellow, primroseprimrose-like flowers clustered near top of the plant

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Class B Noxious Weed

Garden Loosestrife (Lysimachia vulgaris)

Class B Noxious Weed

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

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Class B Noxious Weed

Policeman’s Helmet (Impatiens glandulifera)

Policeman’ Policeman’s helmet spreads along creeks and outout-competes and crowds out other plants Can grow to 10 feet tall in one season

For More Info on Noxious Weeds in King County: http://www.kingcounty.gov/weeds Weed Photo Page: Search by Weed Name

Click thumbnail picture to get more information and photos

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Sasha Shaw King County Noxious Weed Program 206206-296296-0290 [email protected] http://www.kingcounty.gov /weeds http://www.kingcounty.gov/weeds

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