A series of articles on how to identify and manage some common invasive species on Salt Spring Island written by Jean Wilkinson, Stewardship Committee, Salt Spring Island Conservancy.
Spring is slowly arriving, with its longer days, new growth and warm sunshine, but unfortunately it also brings the bright yellow blooms of gorse, and later broom. For people interested in the health of local ecosystems, for those concerned about fire hazards, and for folks with allergies, this heralds a major headache!
Broom and gorse are covered under the Invasive Plants Regulation of the Forest and Range Practices Act, and gorse is also listed as a provincial noxious weed under the BC Weed Control Act. This legislation imposes a duty on all land occupiers to control designated noxious weeds, due to the very serious economic and ecological problems they pose. Kudos to Main Road Contracting for making a special effort to mow the gorse along many Salt Spring roadways this spring before it set seed. This is a great start to a local “Get Rid of Gorse” campaign, and hopefully all property-owners will do their part while it’s still possible to eliminate this fast-spreading invader from our island. With its sharp thorns and aggressive dense growth, gorse is a huge problem in some regions, but it is currently limited to fairly small areas of Salt Spring.
Unfortunately, Scotch Broom is very widespread. Other species such as Portuguese Broom (Cystus striatus) Spanish Broom (Sparitum junceum) and French Broom (Genista monspessulana) are less common, but potentially invasive in this area. Please don’t plant them! There are many lovely low-maintenance, non-invasive plants to choose instead.The Salt Spring Conservancy, in co-operation with CRD and PARC, is holding a free “Drop-Off Day” for invasive plants on May 14. So start Broom-Busting and Getting Rid of Gorse (and other invasives) in your neighbourhood now!!
Scotch Broom and Gorse – QUICK FACTS ABOUT THESE HORTICULTURAL BULLIES
Identification – Cystus scoparius and Ulex europaeus– vigorous perennial shrubs 1 to 3 metres tall with tap-root, woody photosynthetic stems, small evergreen leaves, and bright yellow pea-like flowers. Hairy seed-pods ripen from green to dark brown or black. Mature gorse has distinctive long thick spines. Broom plants live 15-20 years, but gorse may live up to 45 years.
Impacts –Broom and gorse out-compete native species in sunny locations, and prevent the growth of nearby plants by releasing toxins into the soil, thus reducing plant biodiversity and forage for wildlife. They can form dense, impenetrable thickets which reduce access for recreation, impact Garry Oak woodlands and limit movement of large wild and domestic animals. They invade pastures and replace forage plants, and can impair forest regeneration in logged areas. Both species contain volatile oils and create a serious fire hazard.
Found –in grasslands, pasture and rangelands, roadsides, forest clearings, coastal bluffs and other open, disturbed areas.
Spreads – each mature plant produces thousands of seeds which can remain viable up to 50 years. Mature seed-pods split and expel broom seeds up to 5 metres, and gorse seeds at least a metre. Seeds are spread widely by ants, mammals, birds, water, people, vehicles and machinery. Gorse is reported to also spread by rhizomes.
Prevent – Infestations develop easily when soil is disturbed, so avoid this as much as possible. Plant competitive species in susceptible areas to provide shade and thus inhibit germination of broom and gorse seeds.
Control – Grazing by goats and chickens can be effective in reducing infestations. Stems thinner than a pencil can be pulled when the soil is wet. Avoid disturbing soil by placing feet beside plant while pulling, and tamping down afterwards. Larger plants and those growing on rock should be cut at or below ground surface with loppers or pruning saw. To reduce re-growth, cut during bloom before seed-set, or during a drought. Promptly apply wood mulch and phosphorous-rich fertilizer, and re-vegetate with competitive grasses, alternative shrubs or red alder. Monitor area and repeat for 3 to 5 years. Fire is sometimes used to control gorse, but plants can re-sprout and seeds in the soil often germinate following a burn. Although not a preferred method, for persistent infestations herbicides can be applied to gorse stumps or new shoots, as part of an integrated approach.
Disposal – Cuttings are extremely flammable, and will leach toxins into the soil. Small amounts with no seeds can be scattered or piled in shady spots. Large amounts can be chipped or taken to the landfill. Avoid spreading seeds by putting cut or chipped material in strong garbage bags or on tarps in securely covered loads.
Alternatives – (Grows in * sun, + part shade, or # full shade, M = Moist soil, D = Dry soil, DT =Drought Tolerant) Nootka Rose *+M; Tall Oregon Grape *+D,DT; Salal +#M,DT ; Salmonberry *+#M,DT; Thimbleberry *+M,DT; Mountain Mahogany *D,DT; Snowberry *+#D, DT; Red Flowering Currant *+D,DT; Saskatoon *+D/M; Golden Currant *D,DT; Mock Orange *D,DT; California Lilac *D,DT; Forsythia *M,DT; Winter Jasmine *+# M,DT; Japanese Kerria *+# M/D; Hardy Dwarf Broom (Genista lydia) *D,DT; Warminster Broom (Cystisus x praecox) *D, DT; Yellow/Pontic Azalea *#M; Blue Spirea *D/M; Hebe *D.
More Info: Salt Spring Island Conservancy Stewardship Committee 250-537-4877, Coastal Invasive Plant Committee www.coastalinvasiveplants.com , Invasive Plant Council of B.C. www.invasiveplantcouncilbc.ca