Carduus pycnocephalus

Carduus pycnocephalus_Italian thistle_JM DiTomaso
Photo courtesy Joseph DiTomaso

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

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.