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Noxious weeds

King County, Washington

To offer a suggestion or report an error on the King County Noxious Weeds website, please contact Sasha Shaw, education specialist.

Scotch broom
Cytisus scoparius

History and impact

Scotch broom flowers - click for larger imageThis familiar plant, also known as Scot's Broom, is an invasive flowering shrub that grows commonly throughout the Puget Sound region. Originally introduced from Europe as an ornamental and for erosion control, it is highly aggressive and forms dense, monotypic stands which reduce wildlife habitat and hinder revegetation of upland sites and wetland buffers.

Legal status in King County, Washington

Public and private landowners are not generally required to control infestations of Scotch broom that occur on their property in King County, Washington, with the exception of the highway right-of-way of I-90 east of mile post 34 and on the right-of-way of Highway 2 where it dips down into King County before crossing Stevens Pass, in order to reduce its spread to neighboring Kittitas and Chelan Counties. Scotch broom is a Class B Noxious Weed in Washington, first listed in 1988.  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 the limited area described above 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 in 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 also on the Washington quarantine list (known as the prohibited plants list) (external link) 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.

Biology and morphology

Scotch broom stems and leaves - click for larger imageScotch broom is loosely branched with green, slender ribbed branches and small, simple leaves up to half an inch long. It grows from 3 to 10 feet in height. The bright yellow flowers are pea-like, about three-quarters of an inch long. Its seed is borne in dark brown to black hairy, flattened pea-like pods, which when ripe, burst and scatter seeds for yards. Scotch broom grows primarily in open, dry meadows and along roadsides. It is often confused with Spanish broom, which looks similar but is easily distinguished by its rounded, bright green stems, fragrant blossoms, and later flowering time.

Additional information on scotch broom

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

Because scotch broom is so widespread, property owners in King County are not required to control it and we are not generally tracking infestations. We can provide advice on how to control scotch broom, but there is generally no legal requirement to do so.

Scotch broom photos - click thumbnail for larger image

Scotch broom in a field - click for larger image Scotch broom flowers closeup - click for larger image Scotch broom flowering - click for larger image Scotch broom stems with flowers - click for larger image
Scotch broom in March with buds - click for larger image Young Scotch broom - click for larger image Scotch broom variety - click for larger image Scotch broom galls - click for larger image

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).