A perennial, evergreen shrub, spanish broom can be mistaken for Scotch broom (Scot's broom) but is distinguished by its fragrant flowers and round stems. Spanish broom is a noxious weed because of its prolific seed production and aggressive replacement of native plants.
Legal status in King County, Washington
As a Class A noxious weed, its eradication is required in King County and throughout Washington State. Although Spanish broom was formerly sold in Washington State as an ornamental, this is no longer legal because this species is 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
Spanish broom can grow 6 to 10 feet tall, generally prefers low-nutrient, rocky or sandy soils in full sun, and is most often found escaping into disturbed areas such as roadsides, exposed hillsides, trails, parks and vacant lots. The mainly leafless stems branch off at the top, ending with clusters of flowers on leafless racemes (stalks). The leaves are simple and one-parted (as compared to the three-parted leaves of Scot's broom) and are alternate and less than 1 inch long. The leaf shape is linear to lanceolate, and hairs are present on the lower surface. Fragrant, bright yellow and pea-shaped, approximately 1 inch long, the flowers grow in clusters at the branch ends on stalks that can be 18 inches long. They can bloom from July to frost. The fruits are hairy seed pods, flat and linear, up to 3 inches long. Spanish broom spreads by seed.
Additional information on spanish broom
What to do if you find this plant in King County, Washington
Please notify us if you see spanish broom 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. We map all known locations of regulated noxious weeds such as spanish broom in order to help us and others locate new infestations in time to control them.
Spanish broom photos - click thumbnail for larger image