Noxious weeds in King County, Washington

Noxious weeds are a danger to our environment and the economy. These introduced species cost our region millions of dollars in lost agricultural production, environmental degradation and added maintenance costs. Once invasive plants spread to natural areas, they harm native plants and wildlife and can be impossible to eradicate.

poison-hemlock - click for more information — Poison-hemlock

tansy ragwort - close for more information — Tansy Ragwort

garlic_mustard_flowers_above_small — Garlic mustard

Search for other weeds

Identify and learn about weeds and invasive plants

Photo guide and index to weed information pages - Look up specific weeds to learn about each plant's impacts, growth, control methods and identification
Weed lists and laws - King County Weed List, definition of noxious weed, Washington State Weed Law
- 2019 King County Weed List - changes for 2019 include poison-hemlock control requirement on public land and updates to botanical names for some species including tansy ragwort (now called Jacobaea vulgaris)
Fact sheets, brochures, reports and publications - Download weed fact sheets, brochures, slideshows and reports (publicaciónes en español)
Classes and workshops - calendar of upcoming noxious weed classes
Knotweed control videos - learn how to control knotweed and borrow a stem injector
Fairs and events calendar - calendar of noxious weed information booths; experts will be on hand at these events
Healthy Lands Project - resources and events for conservation and stewardship
- Invasive Weed Workshop and Seola Pond Project Open House, Nov. 21
- Seola Pond Volunteer Work Party, Dec. 7
School resources - free classroom programs available for schools in King County
Noxious Weeds blog - Weed of the Month, weed control tips, and other timely information, news and updates

Locate noxious weeds in King County

Maps - view the spread of noxious weeds in King County - see where noxious weed infestations have been found near your location

Report an infestation

Report a noxious weed in King County, Washington with our web form or mobile app. We need your help to find early infestations while we still have a chance to stop them, and to learn more about where weeds are impacting people and the environment in King County.

Control noxious weeds

Best Management Practices and Regulatory Guidelines
Weed control tips - how to control weeds, Best Management Practices, Integrated Pest Management
Knotweed control video - four short videos on knotweed control techniques, including stem-injector instructions

Participate

Join the King County Noxious Weed Control Board
- Share your ideas and feedback at a public Board Meeting
Become a weed watcher - volunteer to spot invasive plants in remote areas and on lakes before they become established
- Lake Weed Watchers
- Trail Weed Watchers
Volunteer to fight invasive weeds and restore parks

To contact us, please see the staff directory for the King County Noxious Weed Control Program, call 206-477-WEED (206-477-9333) or send us an e-mail. Program offices are located in the King Street Center Building at 201 S. Jackson St., Suite 600, Seattle, WA 98104.