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Plants of waste places, roadsides, untended landscapes around buildings.  Flowers June to October.  Not native.

Annual or biennial.  Taprooted.  Stems are soft, glabrous and glaucous, sometimes glandular near inflorescences; sometimes branching from near plant base.  Sap is milky white.  Typical height is 1 to 3+ feet.

The overall inflorescence is diffuse, with a terminal inflorescence and from 1 to several small branch inflorescences, each containing a few flower heads subtended by leafy bracts.

Flower heads are ligulate, 1.5-2.5 cm wideFlorets are bisexual and fertile, 80+ per headCorollas are bright yellow, comparatively short, but evident.  Involucres are cylindrical, becoming greatly swollen toward the base as fruits developPeduncles, involucral bracts and branchlets may be glabrous or glandular; if glandular, then with minute, stalked glands.

Basal leaves may be present at flowering.  Leaves generally are highly variable: spatulate, oblong, lanceolate or oblanceolate, either shallowly or deeply lobed, and with wavy (i.e., not flat), prominently spine-tipped margins.  Upper leaf surfaces are glabrous, often glossy.  Leaf bases have conspicuous, rounded auricles that curl around the stem or branch.

Cypselae are ellipsoid, flattened, not beaked, with 3-5 prominent veins on each faces; faces not ridged between veins.

Similar species:  Sonchus oleraceus and Sonchus arvensis.  Also, refer to my article on Lactuca for additional comparisons.

Notes:  Where S. asper and S. oleraceus co-occur, they may cross, producing progeny with intermediate leaf characteristics (e.g., presence or absence of lobes, dull or glossy leaf upper surfaces, auricle orientation) .  However, S. asper tends to have more prominent, sharper spines than S. oleraceus.  If in doubt, check the cypselae.  S. oleraceus has cypselae with minute ridges (rugose) between the veins, which S. asper lacks.

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