This Class A noxious weed has a limited distribution in Washington and eradication is required. The largest field infestation in Washington State is from Pend Oreille County, where control work on a 10 acre site has been in progress since 1990.

Bighead knapweed is a perennial herb with single yellow, globe shaped flower heads that are about 1 - 3 inches in diameter. It grows on sturdy stock, reaching 5 feet tall. This plant spreads by seed and it has the capabilities to establish in natural areas, particularly in high alpine meadows.

This plant is sometimes found as a garden ornamental. However, it is on the WSDA quarantine list (144 KB Acrobat file, 21 seconds on 56K modem) and it is illegal to buy, sell or offer for sale in the state of Washington. For more information about bighead knapweed, please see the written findings of the WA State Noxious Weed Control Board.

Also, please read the informative Selected Knapweeds of Washington brochure (316 KB Acrobat file, 46 seconds on 56K modem).

If you find bighead knapweed in King County, please notify us through our online infestation form.

To find out where we have records of this weed in King County, use our interactive noxious weed map and search for bighead knapweed.