Weed of the Week: Sulphur Cinquefoil
Often mistaken for marijuana and ornamental strawberry plants because of its five stalky leaflets, sulphur cinquefoil (Potentilla recta)
is known among First Nations for its edible fruit and healing properties on open sores. Making it less popular, however, is its invasiveness in southern British Columbia rangelands and pastures.
Sulphur cinquefoil infestations are impacting native plant diversity and the agriculture industry in BC with a powerful punch. In fact, the Latin word Potentilla, is derived from the word potens, meaning powerful. The name alludes to the medicinal value of sulphur cinquefoil; however, this can also apply to its ability to out-compete desirable forage plants that are crucial to wildlife and livestock. Being unpleasant to taste, sulphur cinquefoil plants are avoided, thus allowing them to out-compete nearby forage crops and native vegetation.
Even without grazing, sulphur cinquefoil out-competes forage grasses over time if it is not controlled, significantly reducing pasture productivity. Every year, BC farmers and ranchers lose an estimated $50 million in crop revenue, and then also pay several million dollars more for control measures, such as herbicides and cultivation, to combat invasive plants. Invasive plants grow rapidly and spread quickly, causing damage to the environment, economy and our health. They are also the second greatest threat to biodiversity after habitat loss, according to the International Union for Conservation of Nature (IUCN).
Also referred to as ‘rough-fruited cinquefoil,’ sulphur cinquefoil is a perennial commonly found in grasslands, shrubby areas, dry open forests, and disturbed sites such as roadsides, pastures, and rangelands. Sulphur cinquefoil is one of over 20 cinquefoil species, most of which are native to BC. Sulphur cinquefoil is a member of the Rose family, identifiable by pale yellow flowers, each with five heart-shaped petals, and hairy leaves that have five to seven leaflets.
Sulphur cinquefoil is native to southeastern Europe and southwestern Asia, with its initial introduction to North America before 1900. Spreading profusely, its range now consists of the entire North American continent, only absent in the northern most part of Canada and Alaska.
In BC, the first collection of sulphur cinquefoil was recorded on Vancouver Island in 1914. Being the terminal for the transcontinental railway, this is likely what enabled its early spread. By 1940 plants were reported in the southern Cariboo, northern Okanagan, and the Kootenays. Current populations extend along the southern portion of the Province, reaching as far north as the Cariboo.
Sulphur cinquefoil is an effective invader through ample seed production; a single plant can produce up to 1,600 seeds. Seeds may only survive up to two years, but they disperse effectively on or through the digestive system of birds, wildlife, and livestock. Seeds can also spread in mud caught in tire tread or undercarriages of vehicles and machinery, or by being picked up on hooves or hair. Additionally, plants spread with new shoots that emerge from the decaying main root, allowing it to live up to 20 years. Thus, hand-pulling the entire root system is the most effective way to remove small infestations.
Infestations are commonly found with invasive diffuse knapweed (Centaurea diffusa) and leafy spurge (Euphorbia esula). Evidence is showing its ability to out-compete native as well as other invasive plants, though more research is necessary to explore its level of competitiveness.
Research is underway to determine the potential of controlling sulphur cinquefoil with natural agents such as insects; however, the close association of this invasive plant with native cinquefoil species and ornamental strawberries may limit this approach.
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