Vascular Plants - Asteraceae - Sonchus:
Sonchus asper
Page Author: Don Knoke
spiny sow-thistle, prickly sow-thistle, spiny-leaf sow-thistle 
Blooms: July - October
Habit: herb
Duration: annual
Origin: Introduced from Europe
Distribution: Cosmopolitan; common in the Pacific Northwest
Habitat: Disturbed areas, roadsides, gardens
Species Description:

General: Glabrous annual 1-10 dm. tall, with milky juice.
Leaves: Leaves quite prickly margined, usually pinnatifid, but frequently obovate and lobeless, with rounded (not acute) auricles, progressively reduced and less divided upward.
Flowers: Heads several in a somewhat flat-topped inflorescence, 1.5-2.5 cm. wide; fruiting involucre 9-14 mm. high; corollas all ligulate, yellow.
Fruits: Achenes with 3 prominent longitudinal ribs on each face, but not wrinkled.

Distinguishing Characteristics: 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
Synonyms:
Sonchus asper (L.) Hill ssp. asper
Sonchus oleraceus L. var. asper L.

Treated in Flora of the PNW as:
Sonchus asper
Additional Resources:

PNW Herbaria Specimens: View list of Sonchus asper specimens in the Consortium of Pacific Northwest Herbaria database.

WTU Herbarium Specimens: View list of Sonchus asper specimens in the WTU Herbarium database.

Washington Flora Checklist: Sonchus asper treatment.

E-Flora BC: Sonchus asper atlas page.

CalPhotos: Sonchus asper images.

USDA Plants Database: Sonchus asper.
Additional photographs of Sonchus asper:
(click on a thumbnail to view larger photo)

Ben Legler, 2004

Ben Legler, 2004

Ben Legler, 2004

Ben Legler, 2004

Ben Legler, 2004

Ben Legler, 2004

Ben Legler, 2004

Ben Legler, 2004

G. D. Carr, 2002

G. D. Carr, 2002

Craig Althen, 2010

Craig Althen, 2010

Paul Slichter, 2009

Paul Slichter, 2009

Paul Slichter, 2009
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Washington Native Plant Society
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