| Canada thistle | USDA PLANTS Symbol: CIAR4 U.S. Nativity: Exotic Habit: Forbs/Herbs |
| Cirsium arvense (L.) Scop. |
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Taxonomic Rank: Magnoliopsida: Asterales: Asteraceae |
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| Synonym(s): Californian thistle, creeping thistle, field thistle | |
| Native Range: Europe (BAIL); | |
Canada thistle is a tall, erect, spiny, perennial, herbaceous plant that grows to 4 ft. (1.2 m) tall. It has an extensive creeping rootstock. The leaves are lance-shaped, irregularly lobed, 2-6 in. (5-15 cm) long with prickly margins. The stems are ridged and hairy. The flowers are purple to white and can be up to 0.5 in. (1.8 cm) in diameter. Flowering occurs in late June to August. The small fruit, called achenes, are 1 to 1.5 in. (2.5-3.8 cm) long and have a feathery pappus which allows them to be dispersed further by wind. Numerous species of thistle occur in North America, and while some are invasive, many are native. Often the species are difficult to distinguish. Canada thistle can invade a variety of open habitats including prairies, savannas, fields, pastures, wet meadows and open forests. It forms dense stands which can shade out and displace native vegetation. Once established it spreads rapidly and is difficult to remove. Canada thistle is native to Europe and Asia and was accidentally introduced to North America in the 1600s. |
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Identification, Biology, Control and Management Resources
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| Selected Images from Invasive.org | View All Images at Invasive.org |
 Flower(s); Purple and (rare) white flowers in the same field Steve Dewey, Utah State University, Bugwood.org Additional Resolutions & Image Usage |
 Flower(s); Mary Ellen (Mel) Harte, , Bugwood.org Additional Resolutions & Image Usage |
 Flower(s); Steve Dewey, Utah State University, Bugwood.org Additional Resolutions & Image Usage |
 Foliage; Leslie J. Mehrhoff, University of Connecticut, Bugwood.org Additional Resolutions & Image Usage |
 Foliage; Mary Ellen (Mel) Harte, , Bugwood.org Additional Resolutions & Image Usage |
 Infestation; UAF Cooperative Extension Archive, University of Alaska - Fairbanks, Bugwood.org Additional Resolutions & Image Usage |
 Flower(s); Michael Shephard, USDA Forest Service, Bugwood.org Additional Resolutions & Image Usage |
 Plant(s); UAF Cooperative Extension Archive, University of Alaska - Fairbanks, Bugwood.org Additional Resolutions & Image Usage |
 Plant(s); Dan Tenaglia, Missouriplants.com, Bugwood.org Additional Resolutions & Image Usage |
 Plant(s); Peggy Greb, USDA Agricultural Research Service, Bugwood.org Additional Resolutions & Image Usage |
 Flower(s); In a forested setting. Chris Evans, Illinois Wildlife Action Plan, Bugwood.org Additional Resolutions & Image Usage |
 Plant(s); Mary Ellen (Mel) Harte, , Bugwood.org Additional Resolutions & Image Usage |
 Plant(s); Mary Ellen (Mel) Harte, , Bugwood.org Additional Resolutions & Image Usage |
 Infestation; In a pasture Steve Dewey, Utah State University, Bugwood.org Additional Resolutions & Image Usage |
 Infestation; in canola (Rape seed) field near Consort, Alberta Alec McClay, McClay Ecoscience, Bugwood.org Additional Resolutions & Image Usage |
 Plant(s); Britton, N.L., and A. Brown. 1913. Illustrated flora of the northern states and Canada. Vol. 3: 553. USDA PLANTS Database, USDA NRCS PLANTS Database, Bugwood.org Additional Resolutions & Image Usage |
 Plant(s); USDA NRCS. Wetland flora: Field office illustrated guide to plant species. USDA Natural Resources Conservation Service. USDA PLANTS Database, USDA NRCS PLANTS Database, Bugwood.org Additional Resolutions & Image Usage |
| EDDMapS Distribution: This map is incomplete and is based only on current site and county level reports made by experts and records obtained from USDA Plants Database. For more information, visit www.eddmaps.org Alternative content
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 State(s) Where Reported invasive. Based on state level agency and organization lists of invasive plants from WeedUS database. Alternative content
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