Canada Thistle

Cirsium arvensecanthistle_1

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.