Source: California Invasive Plant Council

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Carduus tenuiflorus (slenderflower thistle)

Carduus tenuiflorus
Carduus tenuiflorus
Photo courtesy Joseph DiTomaso

Carduus tenuiflorus and Carduus pycnocephalus (slenderflower and Italian thistles) are tall annuals or biennials (family Asteraceae) located along the California coast, Central Valley, and in Sierra foothill l grasslands. They area very similar in appearance and habitat, but their impacts on native plants are generally minor.

Cal-IPC Inventory rating: Limited

Cal-IPC Resources on Carduus tenuiflorus

Cal-IPC News Articles

  • Pitcairn, M. (2000). All weeds that have approved biological control agents, accidental introductions and others. CalEPPC News. 8.

Cal-IPC Symposium Proceedings

  • None for this species

Other Resources on Carduus tenuiflorus

  • 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.
  • 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.