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Canada thistle (Cirsium arvense) is a difficult to manage perennial that spreads by seeds and rhizomes. Leaves are deeply lobed with spines; leaf margins and bases surround stems making stems look spiny as well. Flower heads are usually purple to pink. Root systems may extend more than 10 feet deep. 

Canada thistle.

(Photo: John Strang, University of Kentucky)

Canada thistle.

(Photo: John Strang, University of Kentucky)

Management:

• Avoid cultivation and spread. 
• Cut or mow plants to help reduce root reserves and starve plants.
• Apply spot applications of herbicides when shoots are at least 10 inches tall and before flowers open when plants are most susceptible to herbicides.

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