Steve Dewey, Utah State University, Bugwood.org
Canada thistle
Cirsium arvense

Canada thistle (Cirsium arvense) is an invasive plant. It was first detected in West Virginia in 1963.

Canada thistle crowds out and replaces native plants, changes the structure and species composition of natural plant communities and reduces plant and animal diversity. This highly invasive thistle prevents the coexistence of other plant species through shading, competition for soil resources and possibly through the release of chemical toxins poisonous to other plants.

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