Burn the Broom?
Scotch broom in the Pacific Northwest and the use of fire as an ecological service.
Sooke, British Columbia (BC) 1850: Captain Walter Colquhoun Grant planted the Pacific Northwest’s first Scotch Broom (Cytisus scoparius) seeds in Sooke. These seeds came from Mr Wylie, the British consul of the Sandwich Islands, or as we know it, Hawaii — another established roothold of scotch broom.
Grant’s first three plants of the yellow flowering ornamental shrub in the pea family (Fabaceae) have since spread around southern Vancouver Island to the point that it “has endangered much of our region’s distinctive rainshadow flora” (Pojar and Mackinnon). BC Invasives reports of serious dangers dense thickets pose including that they:
“ · increase wildfire fuel loads, thereby escalating wildfire intensity;
· obstruct site lines on roads, resulting in increased maintenance costs for removal;
· limit movement of large animals; and
· displace native plant species.”
USES:
Broom gets introduced for ornamental reasons and as an erosion control. Less known uses include brewing the seeds as a coffee replacement and fermenting the flowers to produce wine. Cytisine, an alkaloid that can be extracted from broom is used as a nicotine replacement in products like Cravv. Since broom contains toxic alkaloids that can depress the nervous system and heart, caution is advised in preparing your own brew ;)
CONTROL:
By changing the local soil chemistry broom creates monocultures. Small islands, like the Gulf islands of the Salish Sea, have particularly vulnerable native communities. The Islands Trust Conservancy recommends removing broom when the seeds are not ripe. Further, the soil should be moist to reduce disturbance; broom grows particularly well in disturbed sites. Replanting areas with native plants significantly helps to avoid the recolonization by broom. Prioritizing sites where broom is still sparse and ready to spread as the first to remove before moving to the densest sites, working in towards the concentrated areas makes best use of your time.
Removal of broom presents multiple challenges. When mechanically cut, it often grows back so the process must be repeated. The U.S. Fish and Wildlife Service found using fire as part of their integrated pest management framework effective for controlling the spread of Scotch broom. Using fire in a toolbox that contains mechanical solutions appears to be the most effective control. Some suggest chemical solutions but if avoidable, that should always be advised. Biological controls include insects like the seed weevil (Apian fuscirostre). According to Oregon State University, none of the biological controls, as far as has been studied, impact scotch broom colonies to a sufficient extent.
Similar to broom is Gorse (Ulex europaeus). An additional challenge is the spikiness of gorse. Without fire and tools, it is almost impossible to tear gorse out of the ground. In contrast, young broom particularly on soft soil can be easily removed by hand.
On our Finca in Asturias, my family burns the invasive gorse, indicative of overgrazing from the former landowner. Burning is an underutilized ecological tool. My dad, an organic farmer in tropical Tanzania, employs controlled burns to avoid the build-up of excessive fuel loads in the dry season.
Burning also accelerates new grass growth following the rains as nutrients are released from burns. Close by to the family farm, staff at Mikumi National Park use controlled burns for the usual benefits as well as the additional perk of easier game viewing from the roads.
Prescribed burning may not be a popular choice among current landscape managers in the Pacific Northwest but the traditional stewards of the region understood the ecological service of fire. Not only are we missing out on the environmental benefits of working with fire but we face the ravaging costs of wildfires on our ecosystems and livelihoods as fuel loads build up in our mismanaged forests.
Controlled burns and targeted removal of invasive species present some of the best options to ecologically restore our endangered native ecosystems like the magnificent Garry oak (Quercus garryana) savannahs of southern Vancouver Island.
