Canada Thistle (Cirsium arvense)
Bull Thistle (Cirsium vulgare)
Factsheet
Description
Prickly, short-lived herbaceous perennials from long taproots, growing up to 2 m tall. Profuse purple blooms are followed by fluffy seed heads that disperse in the wind.
Habitat
These Eurasian weeds are common on exposed soils. On Galiano Island, they are common in forest clearings, roadsides, and disturbed areas.
Impact
Thick patches are unpleasant to move through once established and can persist, hindering native plant regeneration.
Management
Wear gloves and thick clothing to prevent cuts from prickles. Small plants can be hand-pulled from the basal rosette; ensure that the entire taproot is removed. Larger plants can be mowed and left on the ground prior to flowering. Once plants flower, flower heads can be cut, bagged, and burned.
Our Experience
Thistles typically do not occur on a site unless it has been recently disturbed. Prevent establishment of thistles by limiting soil disturbance. Typically, a site that develops a thistle population will, over time, develop a cover of introduced grasses and/or shrubs. These other species are often more important to control than the thistles themselves.