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
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.

Identification, Biology, Control and Management Resources

Selected Images from Invasive.orgView All Images at Invasive.org


Flower(s); Purple and (rare) white flowers in the same field
Steve Dewey, Utah State University, Bugwood.org
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Flower(s);
Mary Ellen (Mel) Harte, , Bugwood.org
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Flower(s);
Steve Dewey, Utah State University, Bugwood.org
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Foliage;
Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
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Foliage;
Mary Ellen (Mel) Harte, , Bugwood.org
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Infestation;
UAF Cooperative Extension Archive, University of Alaska - Fairbanks, Bugwood.org
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Flower(s);
Michael Shephard, USDA Forest Service, Bugwood.org
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Plant(s);
UAF Cooperative Extension Archive, University of Alaska - Fairbanks, Bugwood.org
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Plant(s);
Dan Tenaglia, Missouriplants.com, Bugwood.org
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Plant(s);
Peggy Greb, USDA Agricultural Research Service, Bugwood.org
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Flower(s); In a forested setting.
Chris Evans, Illinois Wildlife Action Plan, Bugwood.org
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Plant(s);
Mary Ellen (Mel) Harte, , Bugwood.org
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Plant(s);
Mary Ellen (Mel) Harte, , Bugwood.org
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Infestation; In a pasture
Steve Dewey, Utah State University, Bugwood.org
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Infestation; in canola (Rape seed) field near Consort, Alberta
Alec McClay, McClay Ecoscience, Bugwood.org
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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
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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
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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
 


State(s) Where Reported invasive.
Based on state level agency and organization lists of invasive plants from WeedUS database.

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U.S. National Parks where reported invasive:
Antietam National Battlefield (Maryland)
Badlands National Park (South Dakota)
Blue Ridge Parkway (North Carolina)
Catoctin Mountain Park (Maryland)
Colonial National Historical Park (Virginia)
Craters of the Moon National Monument (Idaho)
Devils Tower National Monument (Wyoming)
Dinosaur National Monument (Colorado)
Grand Canyon National Park (Arizona)
Great Smoky Mountains National Park (North Carolina & Tennessee)
Harpers Ferry National Historical Park (West Virginia)
Indiana Dunes National Lakeshore (Indiana)
Manassas National Battlefield Park (Virginia)
Monocacy National Battlefield Park (Maryland)
Redwood National Park (California)
Rocky Mountains National Park (Colorado)
Saint Croix National Scenic Riverway (Wisconsin)
Theodore Roosevelt National Park (North Dakota)
Yellowstone National Park (Wyoming)



Invasive Listing Sources:
Alabama Invasive Plant Council
California Invasive Plant Council
City of Ann Arbor Michigan Parks and Recreation
Commonwealth of Pennsylvania, Department of Conservation and Natural Resources, 1994.
Connecticut Invasive Plant Working Group
Delaware Natural Resources and Environmental Control, 2004
Faith Campbell, 1998
Forest Service-Alaska, 2004
Hoffman, R. & K. Kearns, Eds. 1997. Wisconsin manual of control recommendations for ecologically invasive plants. Wisconsin Dept. Natural Resources, Bureau of Endangered Resources. Madison, Wisconsin. 102pp.
Indiana Native Plant and Wildflower Society
Jil M. Swearingen, Survey of invasive plants occurring on National Park Service lands, 2000-2007
John Randall, The Nature Conservancy, Survey of TNC Preserves, 1995.
Kentucky Exotic Pest Plant Council
Maryland Cooperative Extension Service.  2003. Invasive Plant Control in Maryland. Home and Garden Information Center, Home and Garden Mimeo HG88. 4 pp.
Maryland Department of Natural Resources, 1994
Mid-Atlantic Exotic Pest Plant Council, 2005
Missouri Department of Conservation,
National  Wildlife Refuge Association, Silent Invasion: A Call to Action from the National Wildlife Refuge Association, 2002. Washington DC. 17 pp.
Native Plant Society of Oregon, 2008
New Jersey Department of Agriculture, Division of Plant Industry, 2004
Pacific Northwest Exotic Pest Plant Council, 1998
Rhode Island Natural History Society,
Tennessee Exotic Pest Plant Council
Virginia Department of Conservation and Recreation, 2009