Spotted Knapweed

Spotted knapweed is a short-lived perennial or biennial with a first-year basal rosette and upright, branching stems that carry pink to purple flower heads. It can spread aggressively by seed, so its ecological and regulatory status depends on location; [Minnesota Extension](https://extension.umn.edu/natural-resources/forestry-and-wildlife/invasive-species/spotted-knapweed) and the [Minnesota DNR](https://www.dnr.state.mn.us/invasives/terrestrialplants/herbaceous/spottedknapweed.html) describe it as invasive in that region. ## Identification and season Look for deeply divided gray-green leaves and dark-marked bracts beneath the flower heads. Reported mature height is about 2–4 feet, with flowering from summer into fall; timing varies by climate. The Minnesota DNR notes that the subspecies used for regional populations has been treated under more than one name, so this entry retains the assigned species name, Centaurea stoebe, without guessing a subspecies. ## Growing context Sources describe it in open, disturbed habitats, including field margins, gravel areas, and prairie. Its capacity to form dense stands makes it unsuitable for casual planting where it is invasive or regulated; check local weed rules before moving or managing plants. ## Maintenance Prevent seed spread and follow local guidance. Wear gloves and protective clothing when handling, as Minnesota Extension warns that the plant may irritate skin.