Silybum marianum

Silybum marianum_blessed milkthistle_flower_JM DiTomaso
Photo courtesy Joseph DiTomaso

Synonyms: Carduus marianus L., Carduus mariae Crantz, Cirsium maculatum Scop., Cathamus maculatum (Scop.) Lam., Silybum maculatum (Scop.) Moench, Silybum mariae (Crantz) Gray, Mariana lactea Hill

Common names: milk thistle; variegated thistle; blessed milk thistle; Virgin Mary's thistle; Lady's milk; Holy thistle; spotted thistle; cabbage thistle; spotted thistle; St. Mary's thistle; white thistle

Silybum marianum (blessed milk thistle) is a winter annual or biennial with prickly leaves (family Asteraceae). It is widely spread throughout California in overgrazed pastures and along fencelines and other disturbed areas. Blessed milk thistle produces tall, dense stands that outcompete native species.

Cal-IPC Rating: Limited

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.

Other Silybum marianum 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.
  • 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.