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Perennials.  Colony-forming from rhizomes.  Stems are glabrous and glaucous.  Sap is milky white.  Typical height is 3 to 5+ feet.

The overall inflorescence is diffuse, with a terminal inflorescence and from 1 to several small, branch inflorescences, each containing a few flower heads, the terminal one often flat-topped (corymb-like or umbel-like), leafless, with relatively few flower heads per inflorescence.

Flower heads are ligulate, 3-5 cm wide.  Florets are bisexual and fertile, 150 or more per head.  Corollas are bright yellow to yellow-orange.  Peduncles, involucral bracts and the axis of the inflorescence may be glabrous or glandular; if glandular, then with either sessile or stalked glands.  Also, small tufts of short, matted hairs may be present on peduncles and involucral bracts. 

Basal leaves are often present at flowering.  Leaves generally are lanceolate to oblanceolate, lobed or unlobed, and typically prickly-margined.  Leaf bases are auriculate and clasping; the auricles may be curved or straight.

Cypselae are ellipsoid, slightly flattened, not beaked, with 5+ prominent veins on each face, and with numerous minute ridges perpendicular to veins.

Plants of fields, roadsides, thickets, disturbed areas.  Flowers June  to October.  Not native.

[ Two subspecies have been recognized:  Sonchus arvensis  (L.)  ssp.  arvensis, and Sonchus arvensis  (L.)  ssp.  uliginosus.  The distinction between the two subspecies is based on whether the peduncles and involucral bracts have stalked glands or sessile glands.  I've also found some populations to be eglandular (Iacking glands). ]

 

Similar species:  Sonchus asper, Sonchus oleraceus, Picris hieracioides.  Also, refer to my article on Lactuca for additional comparisons.

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