Carduus tenuiflorus (slenderflowered thistle)

Carduus tenuiflorus

Photo courtesy Joseph DiTomaso

Carduus tenuiflorus (slenderflowered thistle) is a tall annual or biennial (family Asteraceae) located along the California coast, Central Valley, and in Sierra foothill grasslands. It is very similar in appearance and habitat to Carduus pycnocephalus (Italian thistle). Its impacts on native plants are generally minor.

Cal-IPC Inventory rating: Limited

Cal-IPC Resources on Carduus tenuiflorus

• California Invasive Plant Inventory Assessment Form (pdf) - Information gathered by Cal-IPC on the impacts, rate of spread, and distribution of invasive plants in California. Does not include management information.
• Cal-IPC News - Articles from our quarterly newsletter. Each issue is available as a pdf. List of articles on Carduus tenuifolius.
• Cal-IPC Symposium Proceedings - Presentations and papers from our annual Symposium.(None for this species.)

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.

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