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Creeping Thistle
Common Name: Creeping Thistle
Scientific Name: Cirsium arvense
Family: Asteraceae
Description
Creeping Thistle was formerly known as Canada Thistle although it is native to Europe, Asia and Africa. This perennial plant can form new shoots from deep and extensive horizontal roots. It is one of the most invasive species in North America and is a noxious weed in most jurisdictions throughout Canada and the USA, including Alaska.
Range in Yukon
Known from just south of Haines Junction and observed in the Labiche River. It has occasionally been found in potted garden plants in Whitehorse.
Similar Species
Elk thistle (Cirsium foliosum) is a rare native species found throughout southern Yukon. It is often persecuted because it is mistaken for an introduced thistle. It is a biennial with a large flower head that grows in wet areas, usually near rivers.
Ecological Impact
Creeping thistle is competing directly for nutrients and water; it also produces chemicals that help displace native vegetation. It is an aggressive agricultural weed that has the potential to reduce crop yields by 100%. Due to its abundant and flammable litter it can increase fire frequency and severity.
Control
Because the root system is usually well developed, it is almost impossible to dig out. Therefore perennial plants require depletion of nutrient reserves in the root system, prevention of seed production and prevention of dispersal. If roots are cut or broken off new plants may sprout. Mowing or cutting to reduce root reserves and seed production should be done a few times a season for several years. When hand pulling use a shovel and remove as much of the root as possible. When cut, flowering plants will continue to produce seeds. Plant material should be put in a clear plastic bag and placed in the sun until the roots and seeds are cooked.
Contact Environment Yukon Government of Yukon Box 2703 (V-5N) Bruce Bennett, Wildlife Viewing Biologist Phone: 867-667-5331 Email: bruce.bennett@gov.yk.ca |
