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History and impact

tall hawkweed - Hieracium piloselloides - click for larger image
Tall hawkweed, and the other yellow-flowered non-native hawkweeds, can be confused with the common dandelion.  However, hawkweeds are much more invasive and difficult to control, especially in remote mountain meadows and wilderness areas. Currently relatively limited in distribution in Washington, tall hawkweed has the potential to pose the same threat to mountain meadows and rangeland habitat as other more well-established non-native invasive hawkeeds. Tall hawkweed closely resembles other hawkweeds on Washington's noxious weed list, in particular yellow hawkweed and queen-devil hawkweed.

Legal status in King County, Washington

Public and private landowners are required to control infestations of tall hawkweed on their property in King County. Tall hawkweed is a Class B Noxious Weed in Washington, in the group of hawkweeds known as meadow hawkweeds (in the subgenus Pilosella).  Tall hawkweed was first added to the weed list in 2013.  Meadow hawkweeds are designated for required control in King County by the Washington State Noxious Weed Control Board and as a group are on the list of Regulated Class B Noxious Weeds in King County. For more information, see Noxious Weed Lists and Laws or visit the website of the Washington State Noxious Weed Control Board.

Identification (see below for additional photos)

  • Resembles a tall, leggy dandelion with many small flowers in a loose cluster near the tops of the stems
  • tall hawkweed - Hieracium piloselloides in bud - click for larger image
    Plants have multiple stems from a single base and can grow three feet or taller
  • Stems and flowers are somewhat hairy
  • Plant exudes a milky sap when stems or leaves are broken
  • Leaves are mostly found at the base of the plant, with a few leaves on the stems
  • Leaves are narrow, smooth on the upper surface and hairy along the edges and the mid-rib on the underside.
Hawkweed identification can be difficult and often requires technical details such as hair types. Also, hybridization between species can make it even more confusing. For a positive identification, you should consult a technical flora on hawkweeds or contact the noxious weed program.

Growth and habitat

Tall hawkweed has a shallow root system and underground creeping stems called rhizomes. New plants can arise from buds on the rhizomes and on the roots.  Tall hawkweed does not form stolons like some of the other yellow-flowered non-native hawkweeds. Tall hawkweed is a perennial and spreads by seeds, root buds and rhizomes. It usually flowers in June and July and sets seed by August.

Tall hawkweed is mostly found in low-nutrient, coarse soils, particularly along roadsides and in outwash areas. It has been documented in King, Snohomish, Cowlitz and Grays Harbor counties.

tall hawkweed - Hieracium piloselloides infestation - click for larger image
Additional information and photos

What to do if you find this plant in King County, Washington

Please notify us if you see tall hawkweed growing in King County. Our program staff can provide the property owner or appropriate public agency with site-specific advice on how best to remove it. Also, because tall hawkweed is not well-established in King County, we have an opportunity to stop it from spreading if we act quickly. We map all known locations of regulated noxious weeds such as tall hawkweed in order to help us and others locate new infestations in time to control them.

Tall hawkweed photos

tall hawkweed - Hieracium piloselloides buds
tall hawkweed - Hieracium piloselloides in bud
tall hawkweed - Hieracium piloselloides infestation
tall hawkweed - Hieracium piloselloides

Report tall hawkweed in King County, Washington

Locate tall hawkweed in King County, Washington

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).