IPMP3.0, Oregon State University, Copyright 2000

Canada Thistle
Asteraceae (Cirsium arvense)


Biology and Management

Registered Herbicides

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Canada Thistle (link to large image)

Canada Thistle (link to large image)

Canada Thistle Rosette Stage Canada Thistle Flowers

Canada Thistle (link to large image)

Canada thistle is a colony forming perennial weed that reproduces by seeds and root buds on spreading lateral roots. Mature plants are woody with grooved stems growing 1 to 4 feet high.   Mature plants have a deep and extensive root system growing down to a meter under the soil surface. Canada thistle reproduces asexually from rhizamatous roots (any part of the root system may give rise to new plants) or sexually from wind-blown seed, which germinates in the late spring or early fall. Seeds may retain viability 4+ years in the soil. New seedlings develop into rosettes.  Purple flowers are produced in July - August. Canada thistle is a problem in perennial and annual crops, rangeland, and minimum tillage systems, such as peppermint.
Mature Canada Thistle Plant Description

This section contains information on identification of the different life stages of Canada thistle.  Select Biology and Management from the Contents Menu for more information on the biology and management, or select Registered Herbicides for the herbicides that are registered to control this weed in mint.