Canada thistle: Cirsium arvense (Asterales: Asteraceae)

Canada thistle
Asterales > Asteraceae > Cirsium arvense (L.) Scop.
Synonym(s): Californian thistle, creeping thistle, field thistle
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

Biological Control of Invasive Plants in the Eastern United States - USDA Forest Service FHTET

Control of Problem Weeds in Range and Pasture - Montana, Utah, and Wyoming Cooperative Extension Services

Element Stewardship Abstract - The Nature Conservancy

Fire Effects Information System - USDA Forest Service, Rocky Mountain Research Station

Invasive Plant Atlas of New England - University of Connecticut

Invasive Plants and Exotic Weeds of Southeast Alaska - USDA Forest Service, Alaska Region

Invasive Plants Field and Reference Guide - USDA Forest Service, Northeastern Area

Invasive Plants of Asian Origin Established in the United States and Their Natural Enemies - Volume 1 - USDA Forest Service

Plant Invaders of Mid-Atlantic Natural Areas - National Park Service & U.S. Fish and Wildlife Service

Selected Invasive Plants of Alaska - USDA Forest Service, Alaska Region

Weeds Gone Wild Fact Sheets - Plant Conservation Alliance's Alien Plant Working Group

Weeds of the Week - USDA Forest Service, Northeastern Area, Forest Health Protection

Selected Images from Invasive.org

Click on each thumbnail to download the image at 1536x1024 resolution or below for available resolutions.

Use 768x512 for Microsoft PowerPoint and use 1536x1024 for Prints and Publications.

Plant(s); Lynn Sosnoskie, University of Georgia, Bugwood.org 768x512	Foliage; Leslie J. Mehrhoff, University of Connecticut, Bugwood.org 768x512	Foliage; Mary Ellen (Mel) Harte, , Bugwood.org 768x512 / 1536x1024
Flower(s); Steve Dewey, Utah State University, Bugwood.org 768x512 / 1536x1024	Flower(s); Purple and (rare) white flowers in the same field Steve Dewey, Utah State University, Bugwood.org 768x512 / 1536x1024	Flower(s); In a forested setting. South Dakota Chris Evans, River to River CWMA, Bugwood.org 768x512 / 1536x1024
Flower(s); Mary Ellen (Mel) Harte, , Bugwood.org 768x512 / 1536x1024	Flower(s); Female flower heads Richard Old, XID Services, Inc., Bugwood.org 768x512 / 1536x1024	Flower(s); Michael Shephard, USDA Forest Service, Bugwood.org 768x512 / 1536x1024
Flower(s); Male flower heads Richard Old, XID Services, Inc., Bugwood.org 768x512 / 1536x1024	Flower(s); Male flower heads Richard Old, XID Services, Inc., Bugwood.org 768x512 / 1536x1024	Fruit(s); Female flower heads Richard Old, XID Services, Inc., Bugwood.org 768x512 / 1536x1024
Plant(s); Dan Tenaglia, Missouriplants.com, Bugwood.org 768x512	Plant(s); Mary Ellen (Mel) Harte, , Bugwood.org 768x512 / 1536x1024	Plant(s); Peggy Greb, USDA Agricultural Research Service, Bugwood.org 768x512 / 1536x1024
Plant(s); Mary Ellen (Mel) Harte, , Bugwood.org 768x512 / 1536x1024	Plant(s); UAF Cooperative Extension Archive, University of Alaska - Fairbanks, Bugwood.org 768x512 / 1536x1024	Infestation; UAF Cooperative Extension Archive, University of Alaska - Fairbanks, Bugwood.org 768x512 / 1536x1024
Infestation; In a pasture Steve Dewey, Utah State University, Bugwood.org 768x512 / 1536x1024	Infestation; in canola (Rape seed) field near Consort, Alberta Alec McClay, McClay Ecoscience, Bugwood.org 768x512 / 1536x1024	Diagram or Graphic; 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 768x512 / 1536x1024
Diagram or Graphic; 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 768x512 / 1536x1024

Invasive Reference(s):

Check Invasive.org for most current lists.

Alabama - IPC List
Alaska - Noxious Weed Law
Arizona - Noxious Weed Law
California - Noxious Weed Law
California - Invasive Plant Inventory
Colorado - Noxious Weed Law
Connecticut - Noxious Weed Law
Delaware - Noxious Weed Law
Illinois - Noxious Weed Law
Iowa - Noxious Weed Law
Indiana - Noxious Weed Law
Kansas - Noxious Weed Law
Kentucky - EPPC List
Kentucky - Noxious Weed Law
Maryland - Noxious Weed Law
Michigan - Noxious Weed Law
Minnesota - Noxious Weed Law
Missouri - Noxious Weed Law
Montana - Noxious Weed Law
Nebraska - Noxious Weed Law
New Mexico - Noxious Weed Law
Nevada - Noxious Weed Law
North Carolina - Noxious Weed Law
North Dakota - Noxious Weed Law
Ohio - Noxious Weed Law
Oklahoma - Noxious Weed Law
Oregon - Noxious Weed Law
Pennsylvania - Noxious Weed Law
Rhode Island - Noxious Weed Law
Rhode Island - Invasive Species Council List
South Dakota - Noxious Weed Law
Tennessee - EPPC List
Utah - Noxious Weed Law
Virginia - Invasive Alien Plant Species
Washington - Noxious Weed Law
Wisconsin - Noxious Weed Law
Wyonming - Noxious Weed Law
Mid-Atlantic - EPPC List
Invasive Plants: Western North America
Invasive Plants: Guide to Identification and the Impacts and Control of Common North American Species
Invasive Plants of the Upper Midwest
Invasive Plant Atlas of New England

Invasive Plants of the United States

Canada thistle

Identification, Biology, Control and Management Resources

Selected Images from Invasive.org

Click on each thumbnail to download the image at 1536x1024 resolution or below for available resolutions.

Use 768x512 for Microsoft PowerPoint and use 1536x1024 for Prints and Publications.

Invasive Reference(s):

Check Invasive.org for most current lists.

External Links


				Bargeron, C.T., C.R. Minteer, C.W. Evans, D.J. Moorhead, G.K. Douce and R.C. Reardon. Technical Coordinators. 2008. Invasive Plants of the United States DVD-ROM: Identification, Biology and Control. USDA Forest Service. Forest Health Technology Enterprise Team. Morgantown, WV. FHTET-08-11.