scoparius – means broom-like, from Latin scopa, meaning ‘broom’

Native range: Western and central Europe

Leaves:

• alternate
• deciduous
• small
• 3 leaflets when near the base of the branches, becoming simple above, pressed close to the branches

Flowers:

• bright yellow, sometimes tinged with purple
• typical legume flower (calyx cup-shaped, upper lip 2-lobed, the lower 3-lobed)
• about 2 cm long
• usually single in leaf axis

Fruit:

• black, flattened pods
• about 4 cm long
• as the pod matures and dries, the two halves tend to warp in different directions, eventually snapping apart audibly and catapulting seeds

Other characteristics:

• unarmed (no spines)
• spindly
• evergreen or deciduous
• to 3 m. tall
• branches green and strongly 5-angled
• forms dense, monotypic stands which reduce wildlife habitat and hinder re-vegetation of upland sites and wetland buffers

Relevant info:

• on Washington’s prohibited plants list (no buy, sell, or transport)
• introduced to Vancouver Island in 1850 by Capt Grant, an immigrant from Scotland, from some seeds he acquired in Hawaii from the British consul
• ‘broom’ is derived from Angle-Saxon brom meaning ‘foliage’
  • applied to shrubs that were used for making ‘besoms,’ which are bunches of twigs used as brooms

Ecology & Adaptations:

• native to Europe
• widespread noxious weed, usually where conditions are somewhat moist, but well adapted to drier soils in western WA (with its moist climate)
• distributed widely throughout much of Washington, especially in lowlands west of the Cascades crest
• British Columbia south to California
• found in open sites, especially common on disturbed sites (e.g., along roads), but also invading natural meadows, thickets and open forest
• at low elevations
• N-fixing bacteria in roots enable the plant to colonize nutrient-poor and disturbed areas
• herbivore defense – produces toxic alkaloids that depress heart and nervous system
• vegetative regeneration – re-sprouts from stump or roots after cutting or fire
• seed dispersal:
  • a plant may produce up to 10,000 seeds/year
  • pods halves snap apart, catapulting seeds away from plant
  • further dispersed by erosion, flowing water, and ants collecting food
  • seeds remain viable in soil from 5–60 years
• control:
  • dig up or remove with a Weed Wrench, although the disturbed soil is then ideal for seed germination
  • older stems that are no longer green or those that are >2” can be cut during drought of late July/August, with less risk of re-sprouting, though seed germination should be monitored
  • large infestations on roadsides and other areas may require treatment with herbicide for 2 years, with monitoring for 10 years