County offers free workshops to help residents tackle tough noxious weeds

Agencies, landowners asked to help stop spread of invasive and noxious plants, including garlic mustard, invasive knotweed and giant hogweed

The County’s Noxious Weed Program is offering a free class on invasive and noxious weeds June 7, from 6:30-8:30 p.m., at the Kent Regional Library, and has scheduled a series of workshops devoted to controlling invasive knotweed – a tough invader that wreaks havoc wherever it establishes a beachhead along a stream or river. Details on all the classes are available at www.kingcounty.gov/weeds.

The County’s “least wanted” list includes plants such as garlic mustard, a Class A Noxious Weed, according to the Washington State Noxious Weed Board, and one of 48 state-listed noxious weeds that the King County Noxious Weed Program is working actively with landowners to control. Noxious weeds are non-native plants introduced to Washington that cause damage to the natural or economic resources of the state.

Large garlic mustard infestations were found in Coal Creek Natural Area in Bellevue and several infestations were found along the Cedar River in 2010. These discoveries generated concern with Noxious Weed Program staff because this particular weed had been primarily limited to just a few Seattle parks.

Garlic mustard is a fast-spreading biennial introduced to North America from Europe that moves quickly into forests, out-competing native understory species.  Perhaps even more insidious, garlic mustard has been shown to reduce beneficial forest soil fungi needed by native trees and shrubs, according to Steven Burke, the County’s Noxious Weed Program manager.

It is likely there are more garlic mustard sites scattered about the County, and Burke is asking for the public’s help in locating new sites. Garlic mustard photos and information are on the county noxious weed website, www.kingcounty.gov/weeds, where discovered weed sites can also be reported.

The King County Noxious Weed Program is part of a statewide effort to detect and respond to noxious weeds such as garlic mustard that harm natural and economic resources.  To help protect the state’s resources, the Washington State Noxious Weed Control Board adopts a statewide noxious weed list each year. Each County’s weed board then adopts its own noxious weed list that establishes which weeds require control by property owners and public agencies.

The King County Noxious Weed Control Board places a priority on preventing new infestations of the most serious noxious weeds, and encourages property owners to work together in stopping the spread of established noxious weeds.

Another high priority target for King County this year is the massive plant called giant hogweed, feared both for its invasiveness and the toxic juice that causes painful, watery blisters and burns on contact. Giant hogweed has leaves that are up to five feet wide and a central flowering stem that reaches 15 feet tall, topped by an impressive umbrella-shaped flower-head, stretching two feet across.

Since 1996, King County’s noxious weed hunters have found more than 1,000 sites with giant hogweed.

“By watching for new sites, returning to known sites every year, and helping landowners control it where needed, we have been able to keep giant hogweed from spreading and we are hopeful that it can be eradicated someday,” Burke said.

The hardest part of fighting uncommon noxious weeds like giant hogweed is finding them, and this is where the public’s assistance is most needed. Burke said park users, homeowners and neighbors report many new sites of giant hogweed and other noxious weeds each year, encouraged through workshops and outreach tables at community events.

The program seeks to teach homeowners how to recognize and control noxious weeds on their own property. Noxious weed information will be on display at several locations this spring and summer:

• May 14, Tukwila's 10th Annual Backyard Wildlife Festival, 9 a.m.–3 p.m., Tukwila Community Center, 12424 42nd Ave. S.
• June 11, Issaquah Farmer's Market, Pickering Barn, Issaquah
• June 15, Sammamish Farmer's Market, 4—8 p.m., Sammamish Commons, 801 228th Ave SE
• June 25, Maple Valley Farmer's Market, 9 a.m.—1 p.m., Rock Creek Elementary School, Maple Valley
• June 28, Renton Farmers Market , 3—7 p.m., Renton
• July 2, Vashon Low Tide Festival, Vashon Island
• July 7, North Bend Farmers Market, Si View Community Center, North Bend
• July 12, Carnation Farmers Market, 3—7 p.m., downtown Carnation
• July 14, Bellevue Farmers Market, 3—7 p.m., First Presbyterian Church of Bellevue, 1717 Bellevue Way NE
• July 22-23, Enumclaw Street Fair, 9 a.m.—8 p.m. both days, downtown Enumclaw
• July 23, Redmond Farmers Market , 9 a.m.—3 p.m., 7730 Leary Way NE, Redmond
• July 31, Auburn International Farmers Market, 10 a.m.–3 p.m., Auburn Station Plaza, Auburn

The entire schedule is available at www.kingcounty.gov/weeds.

Community groups can schedule a presentation on noxious weeds or an information booth at their event by contacting education specialist Sasha Shaw, at 206-296-0290, or sasha.shaw@kingcounty.gov.

Information on noxious weeds, including the King County weed list and the Washington noxious weed law can be found online at www.kingcounty.gov/weeds. For more information on the King County Noxious Weed Board and Noxious Weed Program, call or email Burke at 206-296-0290 or steven-j.burke@kingcounty.gov.

Related information

Noxious Weeds

King County Water and Land Resources