Common Name: Diffuse knapweed
Scientific Name: Centaurea diffusa (Lam.)
All above and below ground parts of the plant must be destroyed. Additionally, no illegal transportation, propagation, or sale of these plants is allowed. Failure to comply may result in enforcement action by the county or local municipality. Minnesota Noxious Weed Law.
Diffuse knapweed is native to Europe. It was accidentally introduced to the U.S. in the 1800s through contaminated seed. An infestation was found in St. Louis County in 2013.
This plant thrives in disturbed habitats such as roadsides, railroad tracks, gravel pits, vacant lots, and heavily grazed pastures. It can tolerate drought, traffic, disturbance, and thin and gravelly soils.
Diffuse knapweed reproduces primarily by seed, and it is a prolific seed-producer. After flowering, the dried plants may break off at the base of the stem and blow about like a tumbleweed, dispersing seed over long distances.
This knapweed is widespread throughout rangeland in the Western U.S. In Minnesota, there is only one known infestation in St. Louis County. View diffuse knapweed distribution in Minnesota.
Diffuse knapweed overtakes and suppresses native vegetation, reducing species diversity and wildlife habitat. It can also increase soil erosion. This plant is allelopathic, meaning it alters the soil chemistry around it to inhibit the growth of other plants. Diffuse knapweed can also cause crop loss and reduced forage for livestock. The spines on the flower heads can damage the mouths and digestive tracts of livestock.