UW Burke Herbarium species comparison

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Onopordum acanthium

cotton thistle, Scotch thistle, Scots thistle
Habit 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.

Onopordum acanthium
Flowering time June-August
Habitat Noxious weed of dry, open areas and stream banks.
Distribution
Occurring chiefly east of the Cascades crest and in the Columbia River Gorge in Washington; British Columbia to California, east across most of North America to the Atlantic Coast.
[WildflowerSearch map]
[BONAP county map]
Origin Introduced from Eurasia
Conservation status Not of concern
Subordinate taxa
O. acanthium ssp. acanthium
Web links 
Unless otherwise noted, all data comes from the University of Washington's Burke Herbarium.



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Choose a data source: Flora of North America, OregonFlora, UW Burke Herbarium

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