Spotted Knapweed (Centaurea stoebe)

Spotted knapweed is a biennial or a short-lived perennial. It has spotted in the name because under its pink flowers, the floral bracts are tipped black and look like spots. It reproduces by seed and over 140,000 seeds by plant. It can grow up to 1.8 metres tall. It is originally from introduced from Europe.

LRISS Category: STRATEGIC CONTROL

Habitat & Ecology

Spotted Knapweed prefers disturbed areas along roadsides, fields and pastures. It prefers well-drained soil and full sun. It does tend to grow in moister habitats than diffuse knapweed.

Impacts

Spotted knapweed is a very competitive invasive that can out-compete native species. Dense stands can form in pastures, roadsides and disturbed areas. It can also cause skin irritation.

Management

Spotted knapweed has many means of control that include biocontrol, mechanical and preventative. There are 12 biocontrol agents have been released to help manage spotted knapweed. Since it only reproduces only by the seed, cutting, mowing and digging can be successful especially if completed before it sets seed. Seeding disturbed areas can prevent new plants from emerging.

References

Province of British Columbia. 2002. A Guide to Weeds in British Columbia.