Carduus acanthoides

Carduus acanthoides_Plumeless Thistle__flower_JM DiTomaso
Photo courtesy Joseph DiTomaso

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.

Rating: Limited

Cal-IPC Resources

  • 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.
  • CalWeedMapper - Statewide maps, climate models, and reports.
  • Cal-IPC News - Our quarterly newsletter. Each issue is available as a pdf.
  • Cal-IPC Symposium Proceedings - Presentations and papers from our annual Symposium.
  • Don't Plant a Pest! - Select your region to find non-invasive alternatives to ornamental species. Also see our statewide brochure on trees.

    Other Resources

    • USDA PLANTS database -
      Federal database with information on identification and distribution, and links to websites in individual states.
    • Jepson Online Interchange for California Flora - Information on taxonomy, biology, and distribution from the UC Berkeley Jepson Herbarium.
    • CalFlora - Distribution information by county based on submitted observations and herbarium specimens.
    • Encycloweedia - Plants rated as noxious weeds by the California Department of Food and Agriculture.
    • CalPhotos - Images of plants taken mostly in California.
    • Natural Resource Projects Inventory - State database with information on resource management projects throughout California. Query by the species of interest.

    Symposium Presentations

    None for this species.

    Cal-IPC News Articles

    • (1993). California Exotic Pest Plant Council draft list exotic plants of greatest concern October 1993. CalEPPC News. 1: 6.
    • Pitcairn, M. (2000). All weeds that have approved biological control agents, accidental introductions and others. CalEPPC News. 8.
    • Richardson, B. (2004). The A-rated north. Cal-IPC News. 12: 4-5,14.