Page authors: Don Knoke, David Giblin
Onopordum acanthium
cotton thistle, Scotch thistle, Scots thistle
WTU specimens
Other herbaria
WTU images

Distribution: Chiefly east of the Cascades in Washington, but also on the west side; introduced throughout nearly all of North America.

Habitat: Noxious weed of dry, open areas and stream banks.

Flowers: June-August

Origin: Introduced from Eurasia

Conservation Status: Not of concern

Description:
General:

Coarse, branching, strongly spiny biennial up to 2.5 m. tall, with a broadly winged stem, the herbage sparsely to densely white-woolly.

Leaves:

Leaves toothed or slightly lobed, sessile or the lower short-petiolate, the blade up to 6 dm. long and 3 dm. wide, smaller upward.

Flowers:

Heads numerous, 2.5-5 cm. wide; involucral bracts all spine-tipped; corollas all tubular, violet to reddish; receptacle flat, fleshy and honeycombed, not densely bristly like Cirsium; pappus of barbellate bristles.

Fruits:

Achenes 4-5 mm. long, tipped with slender bristles.

Accepted Name:
Onopordum acanthium L.
Publication: Sp. Pl. 2: 827. 1753. 1753.

Synonyms & Misapplications:
(none provided)
Infraspecies:
Additional Resources:

PNW Herbaria: Specimen records of Onopordum acanthium in the Consortium of Pacific Northwest Herbaria database.

WA Flora Checklist: Onopordum acanthium checklist entry.

E-Flora BC: Onopordum acanthium atlas page.

CalPhotos: Onopordum acanthium photos.

USDA Plants: Onopordum acanthium information.

9 photographs:
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