The beautiful but invasive and noxious Scotch broom (Cytisus scoparius) probably arrived in Oregon in the mid-1800’s from European shippers who had packed cases of whiskey bound for California with fresh-cut bundles of the plant. Oregon engineers planted the yellow-blooming shrub in sand dunes and along roads to prevent soil erosion, bakers used Scotch broom to clean cooking surfaces of brick ovens, and plant nurseries sold Scotch broom as an ornamental in California starting in the 1860’s.
The plant’s seeds remain viable for more than 30 years, popping from mature pods and being dispersed even farther by ants.
The shrubs form dense patches that destroy wildlife habitat and compete against desirable plants like Douglas fir. The forest industry in Oregon estimates Scotch broom costs $40 million annually in lost production. The International Union for Conservation of Nature considers the plant a serious threat to biological diversity. Its toxins sicken browsing cattle and its pollen creates allergies for some people. Scotch broom and its French, Portuguese, and Spanish relatives are highly flammable.
Public agencies have experimented for decades with mixed results for natural ways to manage Scotch broom, including insects that attack stems, twigs, leaves, and seeds.
Sources: "Cytisus scoparius." Wikipedia. Web. 13 June 2015. https://en.wikipedia.org/wiki/Cytisus_scoparius; "Weed of the Week." Web. 13 June 2015. http://bcinvasives.ca/documents/ScotchBroom_article2009.doc; Otto, Bridget A. "Help eradicate Scotch broom." Oregon Live. The Oregonian, 30 May 2009. Web. 13 June 2015. <http://www.oregonlive.com/hg/index.ssf/2009/05/_richard_old_xid_services.html>.