Carduus pycnocephalus (Italian thistle)

Carduus pycnocephalus

Photo courtesy Joseph DiTomaso

Carduus pycnocephalus (Italian thistle) is a winter annual forb (family Asteraceae) widely distributed in disturbed open sites, roadsides, pastures, annual grasslands, and waste areas in much of California.

Cal-IPC Inventory rating: Moderate

Cal-IPC Resources on Carduus pycnocephalus

• California Invasive Plant Inventory 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.
• Species account from Invasive Plants of California's Wildlands - Includes biology and management information.
• Cal-IPC News - Articles from our quarterly newsletter. Each issue is available as a pdf. List of articles on Carduus pycnocephalus.
• Cal-IPC Symposium Proceedings - Presentations and papers from our annual Symposium. List of articles on Carduus pycnocephalus.
• Weed Worker's Handbook (pdf) - Includes reproduction factors and treatment options.
• California distribution map - Maps based on survey data from county Weed Management Areas. These maps are the product of those working in the field and are not intended to be definitive.

Cal-IPC News Articles

• O'Rourke, B. and J. Horenstein (2009). Tackling invasive plants on California Sept. of Fish & Game lands. Cal-IPC News. 17: 12.
• (1993). California Exotic Pest Plant Council draft list exotic plants of greatest concern October 1993. CalEPPC News. 1: 6.
• Dozier, M. (2007). Shasta County citizens take on weeds. Cal-IPC News. 14: 4-5.
• Kelly, M. (1997). Lessons from the front: Taking stock to avoid surprises. CalEPPC NEWS. 5: 4-7.
• Massera, J. (2001). More about Italian thistle. CalEPPC News. 9: 14.
• Pitcairn, M. (2000). All weeds that have approved biological control agents, accidental introductions and others. CalEPPC News. 8.

Cal-IPC Symposium Proceedings

• Archbald, G. (1998). Mechanical control methods: beyond weed bashing. California Exotic Pest Plant Council Symposium '98. Ontario, CA.
• Boyd, D. (1997). Eucapyptus removal on Angel Island. California Exotic Pest Plant Council Symposium '97. Concord, CA.
• Briscoe, E. and T. Anderson (2000). War on weeds - invasive weed education and outreach program. California Exotic Pest Plant Council Symposium 2000. Concord, CA.
• Clines, J., J. DiTomaso, et al. (2004). Fire working group. California Invasive Plant Council Symposium 2004. Ventura, CA.
• Guerriero, A. (2002). Monitoring Carduus pycnocephalus (Italian thistle) on grasslands in coastal central California. California Exotic Pest Plant Council Symposium 2002. Sacramento, CA.
• Pirosko, C. and S. Schoenig (2004). Forbs working group. California Invasive Plant Council Symposium 2004. Ventura, CA.
• Pitcairn, M. J. and D. M. Woods (1998). Control methods: Biological control. California Exotic Pest Plant Council Symposium '98. Ontario, CA.
• Pitcairn, M. J. and D. M. Woods (1998). Control methods: biological control. California Exotic Pest Plant Council Symposium 1998. Ontario, CA.

Other Resources on Carduus pycnocephalus

• 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.
• The Nature Conservancy Management Summary - Information compiled by TNC land managers. Photos included for some species.
• Encycloweedia - Plants rated as noxious weeds by the California Department of Food and Agriculture.
• CalPhotos - Images of plants taken mostly in California.

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