Scotch Broom
Cytisus scoparius

History and Impact

This well-known 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. Scotch broom is a Class B Noxious Weed in Washington State.  Control is recommended in King County, but not required except for along I-90 east of mile post 34 and on 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.

Biology and Morphology

Scotch 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.

For information on Scotch broom identification and control, please download our Scotch broom weed alert (603 KB Acrobat file).

For detailed information on managing Scotch broom in King County, please read the Scotch Broom Best Management Practices (344 KB Acrobat file). 

Scotch Broom photos - click thumbnail for larger image