Spotted Knapweed

Spotted knapweed (Centaurea maculosa Lam.)

Spottedknapweed is a member of the Aster family, Thistle tribe. Native tocentral Europe, it is a simple perennial that reproduces from seed andforms a new shoot each year from a taproot. The plant can have one ormore shoots up to four feet tall.

Rosette leaves can be six inches long and deeply lobed. Leaves onshoots are smaller and finely divided, becoming smaller toward the topof the shoot, and are covered with fine hair. Flowering heads aresolitary and occur on shoot tips. They are up to one inch in diameter.Flower color usually is lavender to purple. Seed heads bracts are stiffand black-tipped, with five to seven pairs of short, featheryappendages. Seeds germinate in spring or fall. Perennial plants resumegrowth in early spring and bolt at approximately the same time asdiffuse knapweed. Flowering occurs throughout the summer into fall.Spotted knapweed occupies dry meadows, pasture land, stony hills,roadsides, and the sandy or gravelly flood plains of streams and rivers,where soils are light-textured, well drained, and receive summerprecipitation. Spotted knapweed tolerates dry conditions, similar todiffuse knapweed, but will survive in higher moisture areas as well.

This weed is not preferred by elk and severely reduces availableforage on their ranges. Mule deer brows Spotted knapweed during latesummer and fall thereby contributing to the spread of seeds to newlocations. Each plant can produce from 1400 to 2400 seeds each seasonwith over a 90% germination rate. Seeds can remain viable in the soil upto 8 years. Spotted knapweed patches can increase in area up to 27%annually.

Spotted knapweed Fact/Info Sheet (PDF) Click Here

Spotted knapweed rosette
Spotted knapweed budding
Spotted knapweed black marks on seed headSpotted knapweed flower

Look for previous years "skeletons" near the new infestation.  Bag and dispose of the old plants.

Spotted knapweed skeleton