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 (leaf stalks) 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, ligulate.
Plant Trivia: Native of Europe. The genus name Sonchus comes from the ancient Greek word for “hollow” which refers to the hollow stems of the plant.
Field Identification: Has the typical puffball seedpod most associated with dandelions. The two sow thistle species are distinguished by their achenes (seeds). Also, petiole base pairs on S. asper are more or less rounded, whereas those of S. oleraceus are pointed.
Occurrence: Frequent on various soils in fields, waste places, prairies, and open areas. Considered a pest weed in yards and fields.
Bloom Period: Year-round, but peaks 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 