Silybum marianum (L.) Gaertner

Family: Asteraceae, Tribe: Cynareae

Pertinent Synonyms & Notes (particularly those used in California; go to GRIN for other synonyms)

Carduus marianus L., Cirsium maculatum Scop.

Pertinent Common Names (particularly those used in California; go to GRIN for other common names)

milkthistle, variegated thistle

Primary Disseminule Type


Description (diagnostics are in brown)

Fruit a cypsela, broadly oblong to obovate, somewhat compressed, slightly gibbous, cross-section elliptic, 6–8 mm long x 2.8–3.2 mm wide x 1.8–2.2 mm thick. Surface mottled (sometimes creating some striping) black and brown over a yellowish-tan base, smooth to mildly rippled, shiny. Pappus somewhat persistent to eventually deciduous, bristles mostly 15–20 mm long, numerous, cream-colored, flat, outer scabrid, inner fine, all fused at the base to form a ring that detaches as a unit.

Style base broad (ca. 0.9 mm long x 0.9 mm wide), blunt, cylindrical to lobed, surrounded by a yellowish, raised collar 1.4–1.6 mm across.

Fruit attachment scar basal, somewhat obliquely angled.

Risk Assessment (codes in yellow or red indicate cause for concern; assessments are current as of mid-2011; click AUQP, NZBORIC, or NZBPI for access to the most recent versions of these databases and possible assessment changes)