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What is knotweed and how can I get rid of it?

Knotweed is a major problem in King County. This non-native, noxious weed chokes out native vegetation, increases erosion, degrades water quality and hurts habitat for fish and wildlife. It can also damage roads, pipes and building foundations. This workshop teaches participants: how invasive knotweed grows and spreads, how, when and where to control it, how to use and borrow a stem injector for use on your own land, and what to do after you control the knotweed to restore your land.

2021 classes are open for registration (click the date below to sign up): 

June 2, 6:00 pm - 8:00 pm
June 10, 6:00 pm - 8:00 pm

Past classes can be viewed online on the Noxious Weeds playlist of the King County DNRP YouTube channel

After you take the class (or watch the webinar), you can sign up to borrow our knotweed stem injectors for your own knotweed projects!

Can't take a class, but want to borrow a stem injector? No problem. Watch our videos and take a quiz to qualify instead.

For more information contact us by email or phone at 206-477-9333.

worker injecting invasive knotweed - click for more information on knotweed

Related information

Related agencies


Program offices are located at 201 S. Jackson St., Suite 600, Seattle, WA 98104. To contact staff, see the Noxious Weed Control Program Directory, send an email, or call 206-477-WEED (206-477-9333).