Noxious Weeds Profile - Canada Thistle

Names

• English - Canada thistle
• French - chardon des champs, chardon du Canada
• Latin - Cirsium arvense (L.) Scop.

Photos

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Current Status

• Ontario Weeds Act - noxious
• Other provinces - noxious in AB, BC, SK, MB, and QC
• Canadian Federal Seeds Act - Class 3
• U.S. Federal Noxious Weed - no
• U.S. Noxious State Reg - 42 states (incl. Illinois, Indiana, Mich, Ohio, Penn, New York, Minn, Wisc,)

Poisonous/Cautions

• Pub 505 - no
• NE Weeds - no
• Canadian Poison Plant - not listed
• Cornell Poison Plant - not listed

Distribution

• Common in pastures, roadsides and waste areas.

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Growth Habit

• Perennial

Method of Propagation

• Seeds, Wind blown, Roots/rhizome

Control

• Can be controlled by dicamba and glyphosate products. Spray at early bud stage or in early fall. Repeated applications are needed to kill all root buds. 2,4-D gives top growth control only. Light to medium infestations can be controlled with repeated mowing at 21 day intervals.

Other Comments

• Similar to Japanese barberry which does not normally host the rust fungus. Hybids of these two species may host the fungus. Populations are relatively stable and much lower than for European buckthorn. Rust does not occur every year but can cause significant impact in some years.

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Related Links

• Noxious Weeds in Ontario
• Ontario Weed Gallery: Canada Thistle
• Ontario Vegetation Management Association
• Weed Control Act - R.R.O. 1990, Reg. 1096
• Weed Control Act, R.S.O. 1990, c. W.5

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