Cirsium arvense

Quick ID:

• Perennial with purplish pink flowers less that 2.5cm across.
• Prickly stems and leaves.
• Extensive creeping rhizome.

Habitat:

• Deep creeping rhizome that allows it to survive below the cultivation zone.
• A single plant is capable of producing over 6m of rhizome per year.
• Stems up to 120cm tall, are leafy and hollow, becoming hairy with age.
• An individual plant may produce over 40,000 seeds.
• Seeds are viable in soil for up to 21 years.

How It Got Here:

• Introduced from France in the late 1700’s.
• Now found throughout Canada and the northern half of the United States.

Reasons for Concern:

• Canada thistle is an aggresive weed and has the potential to reduce crop yeilds by 100%.
• The rhizomes are unaffected by cultivation as they grow below normal tillage depths.