California Invasive Plant Council

Rhaponticum repens

Synonyms: Acroptilon repens, Centaurea repens

Common names: Russian knapweed, hardheads, creeping knapweed, mountain bluet, Turkestan thistle

Rhaponticum repens (Russian knapweed) is a perennial forb (family Asteraceae) found in isolated patches throughout California. It may have allelopathic properties. This plant is toxic to horses and crowds out native species.

Cal-IPC Rating: Moderate

CDFA Rating: B*

Cal-IPC Assessment

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

• Weeds and climate resilience in Sierra meadows. Brusati, Elizabeth; Johnson, Doug. Vol 24, Issue 1
• Prioritizing Regional Response to Invasive Plants in the Sierra Nevada. Brusati, Elizabeth; Morawitz, Dana; Powell, Cynthia. Vol 19, Issue 2
• Fighting weeds in the Tahoe basin. Donaldson, Sue. Vol 11, Issue 2

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.

• Preventing weed spread via contaminated hay and straw. Clines, Joanna (2005)
• Getting the job done: Working within the regulatory environment at Lake Tahoe to manage weeds. Donaldson, Susan; West, Wendy; Taylor, Kirk (2003)
• How the west was lost: Reconstructing the invasion dynamics of yellow star-thistle and other plant invaders of western rangelands and natural areas. Gerlach, John D. (1997)

Other Rhaponticum repens Information

• CalPhotos - Images of plants taken mostly in California.
• Calflora - See the distribution of this species on Calflora's map of California.
• CalWeedMapper - Distribution information with ability to determine regional priorities.
• Jepson Online Interchange for California Flora - Information on taxonomy, biology, and distribution from UC Berkeley's Jepson Herbarium.
• USDA PLANTS Database - Federal database with information on identification and distribution, and links to websites in individual states.
• Bugwood - National database from the Center for Invasive Species and Ecosystem Health at the University of Georgia.
• EDDMapS - North American distribution based on Early Detection and Distribution Mapping System.

Additional photos