This article is part of a series from the Sea to Sky Invasive Species Council (SSISC) featuring the highest priority invasive species in the Squamish area. SSISC is a non-profit society dedicated to minimizing the threat of invasive species in the corridor.
The 19th century brought about more than the popularity of brick ovens among bakers, consumption of imported whiskey among gold miners, and trading of ornamentals among gardeners. Trading among settlers also drove the invasion of Scotch broom (cytisus scoparius) into North America. More than 150 years after it was introduced, it is still rapidly invading coastal regions of British Columbia.
Scotch broom has spread far beyond the bounds of cultivation and is now considered an invasive plant. Many invasive species, including Scotch broom, contain toxins that can sicken livestock and people when ingested. People tend to rush for the medicine cabinet to combat the uncomfortable allergy symptoms of wheezing and sneezing with the spring arrival of Scotch broom's yellow blooms.
More than an allergic irritant, Scotch broom is a highly competitive evergreen shrub that has photosynthetic stems, enabling year-round growth and allowing it to form impenetrable thickets, invade rangelands and replace desirable plants.
Scotch broom is not only an escaped ornamental - it was also used in fresh cut bundles to package cases of imported whiskey for gold camps across California and northward into B.C. Packaging was readily discarded, scattering hardy seedpods and likely creating new infestations along these corridors.
Once introduced, Scotch broom sprouts through seed dispersal into high-density infestations that are highly flammable and can increase wildfire fuel loads, resulting in escalated wildfire intensity. Dense patches, first purposely established as a soil binder, now obstruct sightlines on roads and require increased maintenance expenses for removal. Because of its affinity for light-dominated, disturbed areas, any disturbance activity, such as road or home construction near infested areas, can enhance its spread.
Scotch broom is identifiable by bright yellow, pea-like flowers and woody stems. Shrubs grow one to three metres in height and have a lifespan of 15 to 20 years. Flat, hairy seedpods are initially green, turning brown or black with maturity.
Mature plants can produce up to 3,500 pods, each containing five to 12 seeds. As seedpods dry, they split and spiral, expelling the contained seeds near the parent plant. Seedpods are hardy, remaining viable in water, soil and gravel for more than 30 years!
Help your community protect local resources by managing invasive plants such as Scotch broom. Now that the Scotch broom is going to seed, it is best to wait until all the seeds have dropped before removing the plant. Remember to cover your skin since broom can be irritating. Hand-pulling small plants or cutting large ones is effective with prompt re-vegetation of competitive, native shrubbery.
Forget dense broom forests for now and go after the single plants, stragglers, and new infestations. Concentrate on areas where you can make a difference and remember to return next year. Stop the spread. Never compost Scotch broom - take it to the Squamish landfill that is taking invasive plants free of charge this year.
For more information on identifying and getting rid of Scotch broom, please contact the Sea to Sky Invasive Species Council at [email protected] or (604) 935-7665. More information is also at www.ssisc.info.
