Silybum marianum

Silybum marianum_blessed milkthistle_flower_JM DiTomaso
Photo: 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?

CDFA Rating: None?


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 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

  • Bugwood - National database from the Center for Invasive Species and Ecosystem Health at the University of Georgia.
  • CalPhotos - Images of plants taken mostly in California.
  • Calflora - Distribution map and records of this species in California.
  • CalWeedMapper - Distribution map of this species in California with ability to determine regional priorities.
  • EDDMapS - Distribution of this species in North America.
  • Jepson Interchange - Information on this plant's taxonomy, biology, and distribution from UC Berkeley's Jepson Herbarium.
  • USDA PLANTS Database - Information on identification and distribution, with links to websites in individual states.
  • Additional photos

    Silybum marianum_flower heads - infestation_copyright2013_NealKramer
    Silybum marianum (milk thistle) flower heads - infestation. Photo: &#169 2013 Neal Kramer
    Silybum marianum_seedling_copyright2013_NealKramer
    Silybum marianum (milk thistle) seedling. Photo: &#169 2013 Neal Kramer
    Silybum marianum_rosette_copyright2008_NealKramer
    Silybum marianum (milk thistle) rosette. Photo: &#169 2008 Neal Kramer