Noxious Weeds Profile - Knapweed spp.
Table of Contents
- Current Status
- Growth Habit
- Method of Propagation
- Related Links
English - spotted knapweed, black knapweed, brown knapweed,
russian knapweed, diffuse knapweed
French - centaurée maculée, centaurée noire, centaurée jacée, centaurée de Russie, centaurée diffuse
Latin - Centaurea maculosa Lam., Centaurea nigra L., Centaurea jacea L., Centaurea repens L., Centaurea diffusa Lam.
Figure 1 - Black Knapweed
Figure 2 - Spotted Knapweed
Ontario Weeds Act - noxious
Other provinces - noxious in Alberta, BC, Sask, Man (Russian); Alberta, BC, Sask, Man (spotted); Alberta, BC, Sask, Man (diffuse);
Canadian Federal Seeds Act - Class 1 (Russian, diffuse, spotted)
U.S. Federal Noxious Weed - no
U.S. Noxious State Reg - 24 states (including Indiana, Mich, Minn, NY); black - 2 states; spotted - 14 states (including Mich, Minn)' brown - 1 state; diffuse - 12 states (all western states)
Pub 505 - no
NE Weeds - no
Canadian Poison Plant - not listed
Cornell Poison Plant - not listed
Mostly found in western Canada and USA. Black is found in southern Ontario. Brown is found mostly in the western areas of southern Ontario. Russian is known to occur in central Ontario. Spotted can be found throughout Southern Ontario especially in Grey and Hastings. Diffuse is not commonly found in Ontario. Frequently grows in shallow top soil areas.
Perennial, Spotted is biennial or short lived perennial
Very difficult to control. Not listed on any labels except
for diffuse knapweed on the Banvel label. Close mowing at the
bud or flowering stage can reduce infestation (June to October)
but flowering stems may regrow. Shallow cultivation is not effective
but deep plowing (18 cm) followed by vigorous establishment
of grasses can reduce the infestation.
For more information:
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