If you live around or have explored Garry Oak ecosystems on southern Vancouver Island, you will probably recognize this aggressive invasive species. For the rest of you, don’t be fooled by its bright yellow, scented flowers.
Scotch broom is a perennial shrub that was brought from Europe for gardening purposes, but has since become seriously invasive within B.C. While it is mostly found in southern coastal B.C., it has also been found in other areas of the province and along the west coast of the United States.
Spotting Scotch broom is relatively simple: it has pea-like yellow flowers, occasionally with red colouring in the middle. Later in the season, it has dark, flat, hairy seed pods. The plant has compound leaves with three small leaflets. The stems, young at first, turn woody and can grow very large over time.
Scotch broom can spread by seed and by lateral bud growth. One plant can produce up to 3500 seed pods, holding up to 12 seeds each. When seed pods dry up, they split open, releasing the seeds into the nearby area. Sometimes, vehicles and machinery can unintentionally spread these seeds.
Disturbed areas are most vulnerable to uncontrolled growth, as scotch broom needs requires sunlight to grow. These sites can be entirely taken over by large scotch broom plants, leaving behind a near monoculture and little chance of survival or establishment for other species. In fact, the plant is most often found by roadsides, in pastures, in clearcuts and other open areas. Scotch broom seeds also stay viable in the ground for decades - some estimates suggest up to 80 years! The ability for Scotch broom to thrive and spread readily makes it a huge threat to biodiversity on the west coast, especially in rare, vulnerable locations such as the Garry Oak ecosystem.
So, here is my challenge to all of you: Get out there and join in the effort of removing this invasive plant! Many non-profit organizations and volunteer groups help to remove Scotch broom, but often lack enough manpower to create significant change. By joining these groups, we can help to mitigate the impact of this invasive plant.
Various options exist for Scotch broom mitigation, ranging from mechanical to biological controls. Plants can be removed by cutting their stems as close to the ground as possible in May, when they are blooming and most vulnerable. It is critical to execute stem cutting at this precise time of year, before they release hundreds of seeds, which can stay viable for many decades. Pesticides can also be used on the stem. Biological control should only be attempted by professionals, and involves introducing a pest of Scotch broom to the plants in order to weaken them.
One example of an organization working to combat the vicious Scotch broom is the Galiano Conservancy Association. Conservancy members - including youth, seniors, international interns, and summer students - work together throughout May to clear as much of this invasive plant as possible from Galiano Island (part of the southern Gulf Islands), and surrounding islets. The volume of invasive plants in this location is too monstrous to eliminate entirely by hand; however, these efforts go a long way to protect the natural ecosystem and control invasive plants. Continued efforts such as these may eventually lead to near eradication of this invasive plant from BC ecosystems.