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Canada Thistle

Species
Cirsium arvense

Canada thistle (Cirsium arvense) is a root-creeping perennial. Thickets of thistle crowd out forage grasses in pastures and rangelands, reducing crop yields and productivity. 

Considered noxious under the BC Weed Control Act, Canada thistle is commonly found on roadsides, cultivated fields, pastures, logged forests, riverbanks, and other disturbed areas. It is a major concern in the Peace River, Omineca and Skeena areas, and is a widespread throughout the province.

Canada thistle has purple or white flowers, with stalkless, spiny, dark-green leaves, growing to 0.3-2 metres in height at maturity.

Canada thistle spreads rapidly through horizontal roots that give rise to large infestation patches nearby and out-competing native plants. Canada thistle develops seeds sparingly and may produce 1,000 to 1,500 seeds per flowering shoot. Best adapted to rich, heavy loam, clay loam, and sandy loam, it grows poorly in shaded conditions, can tolerate saline, wet, or dry soils, but does not tolerate waterlogged or poorly aerated soil. Dispersed primarily by wind, seeds can also be dispersed by water, animals, clothing, equipment, and vehicles. 

TIPS Factsheets

Canada Thistle

Despite its common name, this invasive thistle is not native to Canada, but actually native throughout Europe and Northern Asia. It was likely one of the first weeds introduced by North American settlers in the 1600s as a contaminant in seeds. It grows in circular patches by spreading vegetatively through roots and once established, it spreads quickly replacing native plant.Learn more

Gallery: Canada Thistle

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