Department Header For Noxious Weed Division
Yellowstone County, Montana
Noxious Weed
Weed Information Contact Department

Diffuse Knapweed
(Centaurea diffusa)

Diffuse Knapweed
Photo from Weeds of the West, revised edition

Diffuse Knapweed Rosetta

Diffuse Knapweed Young

Diffuse Knapweed Stem

Diffuse Knapweed Leaf

Diffuse Knapweed Bloom

Diffuse Knapweed Mature

Growth Habit: diffusely branched annual or short-lived perennial, 1 to 2 feet tall.

Leaves: Leaves are pinnately divided.

Stem: Stems are rough to the touch. 1 to 2 feet tall.

Flower: Flowers are white to rose or sometimes purplish; margins of involucral bracts are divided like the teeth of a comb, and bracts are tipped with a definite slender spine. Achenes are brown or grayish; pappus is lacking.

Roots: Elongated taproot

Seeds: Oblong, dark brown or grey with longitudinal lines.

Reproduction: By seed

Habitat: Diffuse Knapweed can be found in pastures, rangeland, roadsides, waste areas, as a highly competitive plant.

Biological Controls:

Herbicides: Tordon, Tordon + 2,4-D, Curtail + 2,4-D, dicamba + 2,4-D, Milestone

Video Supplied By Montana Weed Control Association