Sonchus oleraceus
Family: Asteraceae
Plant Description: Annual with hollow stems and milky sap, to 120 cm high with spiny-toothed leaves 7-20 cm long, alternate. Petioles with a pair of pointed basal “ears,” margins lobed and sharp-toothed. All flowers look like ray flowers, yellow, but with five lobes. Heads corymbose clustered, 1.5-2.8 cm wide, ligulae.
Plant Trivia: Native of Europe
Field Identification: the two sow thistle species are distinguished by their achenes (seed). Petioles base pairs on S. asper are more or less rounded, where as those of S. oleraceus are pointed.
Occurrence: Frequent on various soils in fields, waste places, prairies, and openings. A pest weed in yards and fields.
Bloom Period: Year-round, but peak during Spring and Summer
Plant Use: Goldfinches eat the seeds.
Key to species of Sonchus:
- Achenes smooth…………………………………………………………………………….S. asper
Achenes cross-wrinkled…………………………………………………………..S. oleraceus
stxflora 