Spotted Knapweed
(Centaurea maculosa Lam.)
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MATURE PLANT
* 1-3 feet tall |
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ROSETTE
* deeply lobed |
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FLOWER
* ¾ to 1 inch diameter lavender color |
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INFESTATION
* approx…109 acres in El Paso County | |
Spotted Knapweed, (Centaurea maculosa Lam.) is a member of the Aster family, Thistle tribe. It is a biennial or short lived perennial that reproduces from seed and forms new shoots each year from a taproot. The plant can have one or more shoots up to 4 feet tall. Becoming smaller toward the top of the shoot, leaves are finely divided, and are covered with fine hair. Flowering lavender heads are solitary and occur on shoot tips. The bulb (involucre) below the blossom has stiff points (bracts) but not sharp. The seed head bracts are black tipped, with 5 to 7 pairs of short feathery appendages. The germination of seeds is in the spring or fall.
Spotted knapweed tolerates dry conditions, similar to diffuse knapweed, but will survive in higher moisture areas as well. Found mostly in streams and rivers, where soils are light textured, well drained, and receive summer precipitation, dry meadows, pasture land, stony hills, roadsides, and the sandy or gravelly flood plains.
Spotted Knapweed is a very aggressive plant. Infestation will take over a large area quickly.
Control the plant by keeping it from producing seed. Sheep, goats and cattle will consume younger plants. Avoid overgrazing to preserve competitive grasses. Pulling or spraying is an effective way of controlling Spotted Knapweed. Plant perennial grasses in the fall. Fertilize and irrigate the area to stimulate grass competition.
In accordance with the Colorado Weed Management Act, Spotted Knapweed is one of four weeds that must be controlled.