Skip to main content
King County logo

Himalayan knotweed - Polygonum polystachyum
This aggressive competitor in the Buckwheat Family was introduced from Asia as an ornamental.

Legal status in King County, Washington

Public and private landowners are not generally required to control infestations of Himalayan knotweed that occur on their property in King County, Washington, except in selected areas on the Green River and its tributaries and on the Cedar River and its tributaries, as described on the King County Weed List. Himalayan knotweed is a Class B Noxious Weed in Washington, first listed in 2003. It has not been designated for required control in the county by the Washington State Noxious Weed Control Board, but it has been selected for required control in limited parts of the county by the King County Noxious Weed Control Board. Because control is not generally required in the county, it is on the list of Non-Regulated Noxious Weeds for King County. For more information, see Noxious Weed Lists and Laws or visit the website of the Washington State Noxious Weed Control Board.

This species is on the Washington quarantine list (known as the prohibited plants list) and it is prohibited to transport, buy, sell, offer for sale, or to distribute plants or plant parts, seeds in packets, blends or "wildflower mixes" of this species, into or within the state of Washington. For more information, see Noxious Weed Lists and Laws.

 

Additional information on Himalayan 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).