Centaurea diffusa

Centaurea diffusa_diffuse knapweed_flowerheads_JM DiTomaso
Photo: Joseph DiTomaso

Synonyms: Acosta diffusa (Lam.) Sojak

Common names: diffuse knapweed

Centaurea diffusa (diffuse knapweed) is usually a biennial plant (family Asteraceae) that forms dense infestations. Seeds disperse when stems break off and tumble in the wind. Diffuse knapweed is not very common in California, but is one of the most invasive species in many other western states.

Cal-IPC Rating: Moderate?

CDFA Rating: -*?


Plant Assessment Form - Information gathered by Cal-IPC on the impacts, rate of spread, and distribution of invasive plants in California. Does not include management information.

Species ID Card

Invasive Species ID Card - To support field identification of early detection species, Cal-IPC has designed a set of Species ID cards that can be downloaded, printed double-sided, and trimmed to size.

Weed Management Notes

  • Management Notes - Information on management techniques and effectiveness from the University of California Cooperative Extension’s Weed Research & Information Center.

Cal-IPC Newsletter Articles

Cal-IPC Symposium Presentations

Presentations are linked where available. Where a presentation is not available, find more information by reading the abstract in the Cal-IPC Symposia Archive.

Other Centaurea diffusa Information

  • Bugwood - National database from the Center for Invasive Species and Ecosystem Health at the University of Georgia.
  • CalPhotos - Images of plants taken mostly in California.
  • Calflora - Distribution map and records of this species in California.
  • CalWeedMapper - Distribution map of this species in California with ability to determine regional priorities.
  • EDDMapS - Distribution of this species in North America.
  • Jepson Interchange - Information on this plant's taxonomy, biology, and distribution from UC Berkeley's Jepson Herbarium.
  • USDA PLANTS Database - Information on identification and distribution, with links to websites in individual states.
  • Additional photos

    Centaurea diffusa_flower head (full flower)_ZoyaAkulova
    Centaurea diffusa (diffuse knapweed) flower head (full flower). Photo: Zoya Akulova
    Centaurea diffusa_flower heads_copyright2001_FredHrusa(CDFA)
    Centaurea diffusa (diffuse knapweed) flower heads. Photo: &#169 2001 Fred Hrusa, CDFA
    Centaurea diffusa_rosette_copyright2001_FredHrusa(CDFA)
    Centaurea diffusa (diffuse knapweed) rosette. Photo: &#169 2001 Fred Hrusa, CDFA
    Centaurea diffusa_growth habit_copyright2001_FredHrusa(CDFA)
    Centaurea diffusa (diffuse knapweed) growth habit. Photo: &#169 2001 Fred Hrusa, CDFA