Page authors: Don Knoke, David Giblin
Sonchus asper
prickly sow-thistle, spiny leaf sow-thistle

Distribution: Occurring on both sides of the Cascades crest in Washington, but more common west of the crest; Alaska to California, east to the Atlantic Coast.

Habitat: Forest edge, balds, prairies, roadsides, ditches, wastelots, and other disturbed open areas at low elevations.

Flowers: June-October

Origin: Introduced from Europe

Growth Duration: Annual

Conservation Status: Not of concern

Pollination: Flies, butterflies


Glabrous annual 1-10 dm. tall, with milky juice.


Leaves quite prickly margined, usually pinnatifid, but frequently obovate and lobeless, with rounded (not acute) auricles, progressively reduced and less divided upward.


Heads several in a somewhat flat-topped inflorescence, 1.5-2.5 cm. wide; fruiting involucre 9-14 mm. high; corollas all ligulate, yellow.


Achenes with 3 prominent longitudinal ribs on each face, but not wrinkled.

Identification Notes:

The similar S. oleraceus has leaf margins that are weakly prickly, the lobes on the pinnatifid leaves point backward, the auricles are sharply acute, and the achenes are wrinkled..

Accepted Name:
Sonchus asper (L.) Hill
Publication: Herb. Brit. 1: 47. 1769.

Synonyms & Misapplications:
Sonchus oleraceus L. var. asper L.
Additional Resources:

PNW Herbaria: Specimen records of Sonchus asper in the Consortium of Pacific Northwest Herbaria database.

WA Flora Checklist: Sonchus asper checklist entry.

OregonFlora: Sonchus asper information.

E-Flora BC: Sonchus asper atlas page.

CalPhotos: Sonchus asper photos.

USDA Plants: Sonchus asper information.

54 photographs:
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