Canada Thistle

Cirsium arvense

Family: Asteraceae

Description and Life Cycle

A perennial, spreading by seeds and a horizontal creeping root system. Stems are erect, up to 1.2 m tall, with alternate leaves, 4-21 cm long, divided into deep, irregular, spiny lobes. The leaves are dark green and shiny on the surface with white hairs underneath. Flowers form in clusters on small heads and are rose-purple, pink or sometimes white. Flowering occurs throughout the summer.

Biological Control Agents

• Altica carduorum – Beetle
• Hadroplontus litura - Beetle (weevil)
  
• Larinus planus - Beetle (weevil)
• Rhinocyllus conicus – Beetle (weevil)
• Terellia ruficauda - Fly
  
• Urophora cardui - Fly
  

References

Cranston, R., D. Ralph and B. Wikeem. 2005. Field guide to noxious and other selected weeds of British Columbia. Gov. of BC. 94 p.

Powell, G. W., A. Sturko, B. Wikeem and P. Harris. 1994.  Field guide to the biological control of weeds in British Columbia. B.C. Min. For. Res. Prog.