Invasive plants are considered one of the greatest threats to biodiversity in Canada as they present an enormous risk to native plants and the animals that depend on those plants. Native plant species have existed here for thousands of years and have co-evolved with other species, forming diverse and intricate relationships. Introduced to Vancouver Island in the mid 1800’s, Scotch broom (Cytisus scoparius) is a relatively new arrival to this part of the world and does not share the same harmonic relationships found between native species. In fact, it is considered a highly invasive species that can wreak havoc on the ecosystem in which it exists.
Although Scotch broom’s bright yellow flowers are beautiful when in bloom, broom is a menace! Each plant has the potential to produce up to 20,000 seeds that can survive in drought and fire, and can lay dormant in the ground for up to 40 years. Talk about a resilient plant! Broom grows at an alarming rate, and can reach 1-2 metres high within a year of germination. In addition to forming dense patches that can block out the sunlight, its phenomenal growth rate exerts significant pressure on local resources. If that’s not enough, it has been shown that broom releases alkaloids into the soil which inhibit the growth of other plants. These factors collectively create a hostile environment for other plant species and allow broom to outcompete them for water, nutrients, space, and sunlight. With such an abundance of broomy-vegetation, you would think herbivores would be keen to nibble away at them. Unfortunately, this is not the case. Due to broom’s elevated levels of tannins and alkaloids, it is unpalatable, and even poisonous to most native animal species. Lastly, the high oil content in Scotch broom makes it highly flammable. The presence of broom increases wildfire fuel load and can escalate fire intensity. This is especially concerning with drier and hotter summers on the rise.
So what to do about broom?
Broom sounds like a pretty formidable plant, but believe it or not, it can be stopped.
Cool fact: Qualicum Beach is now 99% broom free through the work of volunteers and with town support.
Broom can be effectively controlled by cutting and/or pulling it any time of the year. However, these are some key tips that help ensure that it stays gone:
Pull small broom plants (< ½ inch in thickness) by hand when the soil is wet. You can do this by putting your feet on either side of the plant and pulling as to not disturb the soil.
Cut broom plants greater than a half-inch in thickness at the base, below radial branching, ideally below the soil level. Note: If while uprooting Scotch broom the soil is disturbed, it will allow the seeds present there to germinate more readily.
The best time to cut a broom plant is when it is in bloom or just before. The plant will have used all its energy to produce flowers and will hopefully become drought-stressed as summer sets in.
Try not to cut broom once it has produced seeds. You’ll likely help the plant spread its seeds with the disturbance.
Replant with native species.
Broom removal on Thetis
Many Thetis Islanders already manage broom on their own properties, and ThINC has been tackling invasive plants in the two nature reserves - Fairyslipper Forest and Moore Hill - for the last couple of years, yet it is only the beginning of the battle with the broom. All disturbed areas - along roadways, under power lines, and in recently cleared land are susceptible to broom and other sun lovin’ invasives. But with a concerted effort (as evident in other communities), it is possible to control invasive species and re-establish native ones for a more robust ecosystem.
A huge thank you to all who joined in on the broom removal party at Fairyslipper Forest Nature Reserve last weekend! A large swath of broom (thousands of plants) were removed near the entrance to Fairyslipper Forest and in pockets throughout the Reserve.
For more on broom, check out the Broombusters website, a resource for all you need to know about broom and broom removal in BC, as well as the Invasive Species Council of BC handy, dandy fact sheet.