California Invasive Plant Council

Carduus pycnocephalus

Common names: Italian thistle

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 Rating: Moderate

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.

Weed RIC 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

• Weed biological control agents approved for California. Pitcairn, Michael J.; Smith, Lincoln; Moran, Patrick. Vol 22, Issue 1
• Taking to the air to locate, prioritize and treat effectively. Burger, Jutta C.. Vol 21, Issue 2
• Tackling invasive plants on California Sept. of Fish & Game lands. O'Rourke, Brianne; Horenstein, Julie. Vol 17, Issue 1
• Shasta County citizens take on weeds. Dozier, Melissa. Vol 14, Issue 4
• More about Italian thistle. Massera, Jack. Vol 09, Issue 2
• Italian thistles: an ominous threat. Cowan, B.. Vol 08, Issue 1
• Lessons from the front: Taking stock to avoid surprises. Kelly, Mike. Vol 05, 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.

• Mapping weeds and rare plants to inform management and conservation in the Zaca and Jesusita fires. Calloway, Stephanie; Schneider, Heather; Knapp, Denise (2018)
• Fire working group. Clines, Joanna; DiTomaso, Joe; Goode, Suzanne (2004)
• Forbs working group. Pirosko, Carri; Schoenig, Steve (2004)
• Monitoring Carduus pycnocephalus (Italian thistle) on grasslands in coastal central California. Guerriero, Anthony (2002)
• War on weeds – invasive weed education and outreach program. Briscoe, Emily; Anderson, Thor (2000)
• Control methods: Biological control. Pitcairn, Michael J.; Woods, Dale M. (1998)
• Mechanical control methods: beyond weed bashing. Archbald, G. (1998)
• Eucalyptus removal on Angel Island. Boyd, David (1997)

Other Carduus pycnocephalus 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.
• Bugwood - National database from the Center for Invasive Species and Ecosystem Health at the University of Georgia.