Prickly Sow Thistle

Sonchus asper

Sonchus asper Photo © by Michael Plagens

Photographed along Mesquite Wash, Maricopa Co., Arizona. Aug. 1, 2009.

ANNUAL: Herbaceous annual that may grow low or taller depending on conditions. Most leaves are basal, with progressively smaller leaves higher on the stems. When broken, stems exude milky sap.

RANGE: A cosmopolitan weed native to Eurasia and now found throughout North America.

LEAVES: Margins of the leaves typically have sharp prickles at the tip of each dentition. During vegetative growth from late winter the leaves grow as a rosette close to the ground.
Sonchus asper Photo © by Michael Plagens
FLOWERS: Small, yellow, dandelion-like flower heads composed entirely of yellow strap-shaped florets. Can flower almost anytime of year when moisture has been adequate for growth.

FRUIT: The achene seeds bear a pappus of many fine capillary bristles at the top and do not have a beak at the top.

ARMED: The prickles can be surprisingly sharp.

Asteraceae -- Sunflower Family

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More Information:

Sonoran Desert Field Guide
Sonoran Desert Places
Sonoran Desert Naturalist Home Page


Copyright Michael J. Plagens, page created 4 Aug. 2009,
updated 1 Feb. 2016.