Silybum marianum |
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milk-thistle |
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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 |
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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.
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Origin | Introduced from the Mediterranean region |
Conservation status | Not of concern |
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