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milk-thistle

Habit Glabrous, herbaceous winter annual or biennial, spiny throughout, the stems 6-15 dm. tall.
Leaves

Leaves pinnately lobed, up to 6 dm. long and 3 dm. wide, petiolate below, becoming sessile and clasping above, spiny margined, marked with white along the main veins.

Flowers

Heads large, globose, terminating the branches;

involucre bracts imbricate in several series, broad, firm, mostly spiny-margined and strongly spine-tipped, the coarse, spreading tips widened at the base;

flowers all tubular and perfect;

corollas purple, with slender tube and 5 long, narrow lobes;

filaments glabrous, united at the base;

receptacle flat, densely bristly;

pappus of numerous, slender, unequal bristles.

Fruits

Achenes flattened, glabrous, about 6 mm. long.

Silybum marianum

Flowering time May-July
Habitat Roadsides, fields, wastelots, and other disturbed areas.
Distribution
Occurring in scattered locations on both sides of the Cascades crest in Washington; British Columbia to California, east across Canada and the southwestern U.S. to eastern North America.
[WildflowerSearch map]
[BONAP county map]
Origin Introduced from the Mediterranean region
Conservation status Not of concern
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