Bull Thistle

Cirsium vulgare

Family: Asteraceae

Description and Life Cycle:

A biennial, spreading by wind-borne seed. It forms a large, flat rosette with a long, fleshy tap root in the first year, and produces a 0.3-1.5m bolt in the second year. The stems are spiny winged and slightly woolly. Leaves are alternate, deeply lobed, with each lobe ending in a long sharp spine up to 1 cm long. The upper leaf surface is deep green and has sharp prickles, while the lower surface is white with small white hairs. Purple flower heads, 3.8-7.8 cm in diameter, occur throughout the summer.

Biological Control Agents

• Larinus planus – Beetle (weevil)
• Rhinocyllus conicus – Beetle (weevil)
• Trichosirocalus horridus – Beetle (weevil
• Urophora stylata – Fly

References

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.