Canada Thistle


Canada Thistle (Cirsium arvense) Sunflower family

A perennial that grows to five feet tall with erect, ridged branching stems. Leaves have sharp spines, are wavy, oblong, alternate on stem with woolly hairs on underside.Leaves arise directly from the stem without a distinct leaf stalk. Flowers are purple-pink in clusters at the ends of branches.

Forms colonies via an extensive horizontal and vertical root system; can eventually cover acres. Also spreads by wind-blown seeds. Young plants appear as basal rosettes that bloom in late summer.

Uncommon in the Kenai Peninsula. Can be found in fields, pastures, forests, along roadsides, ditches, and river banks.Produces allelopathic chemicals that suppress surrounding vegetation.

More information


U.S. Fish and Wildlife Service U.S. Forest Service Kenai Soil and Water Conservation District Kenai Peninsula Borough Homer Soil and Water Conservation District UAF Cooperative Extension Service