IDENTIFICATION
Provincial Noxious. Perennial.
Perennial sow thistle grows on a single stem, branching near the
top. The branches end in large, loose, clusters of yellow, dandelion-like
flowers. Leaves vary in shape and have weak prickles on the edges. Upper
leaves clasp the stem directly. Mature plants contain a bitter milky juice
and grow to 1.5 m tall. Annual sow thistle has smaller flowers.
DAMAGE
Perennial sow thistle is an aggressive, creeping weed that can
severely reduce yields in cultivated fields. It is an alternate host for
several viral diseases. Sow thistle can become a serious problem
on marshes, ponds, and riverbank areas. Chemicals from the roots and decaying
residue from old growth inhibit seed germination of other species.
HABITAT
It is adapted to a wide range of environmental conditions, but is most
competitive in temperate climates with abundant moisture. It can also
grow on dry to moderately dry roadsides, disturbed areas, cultivated fields,
and riverbank areas. It is present in all agricultural regions of British
Columbia and a major concern in the Peace River region.
SPREAD
Seed is spread mainly by wind, but some birds feed on and spread the seeds.
