California Invasive Plant Council

Carduus acanthoides

Synonyms: Carduus fortior

Common names: plumeless thistle; bristly thistle; giant plumeless thistle; spiny thistle

Carduus acanthoides (plumeless thistle) is a tall biennial (family Asteraceae) with spiny leaves that colonizes disturbed open sites, roadsides, pastures, annual grasslands, and waste areas. It can inhibit growth of native plants in its vicinity. Plumeless thistle is uncommon in California, and the California Department of Food and Agriculture has an active program to control known populations.

Cal-IPC Rating: Limited

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

• Eradication in the central Sierra. Cal-IPC. Vol 24, Issue 1
• California Exotic Pest Plant Council draft list exotic plants of greatest concern October 1993. CalEPPC. Vol 01, Issue 4

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.

• Hydrilla: A case study: The state of California’s noxious weed eradication programs. O'Connell, Ross A. (1997)

Other Carduus acanthoides 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.
• CDFA - California official noxious weeds.
• USDA PLANTS Database - Federal database with information on identification and distribution, and links to websites in individual states.