Sonchus oleraceus

Plants of the genus Sonchus are often confused with Cirsium sp. (bull-thistle), probably because they are both called thistles and have spiny leaves. Sonchus is easily distinguished from look-alikes by the presence of milky sap. Distinguished from S. asper by the fewer and more reduced spines along the leaf margins.

Seeds germinate poorly at constant temperatures. Germination is good at alternating temperatures of 50-77 degrees F (10-25 C) (Maguire and Overland 1959). In tests by Hocombe (1961) seeds germinated well on the soil surface and not at all when planted 1/4" deep, indicating a light requirement. Dorph-Petersen (1924) reported seeds, stored dry, last 9 years with a gradual decline in viability.

Found in disturbed ground throughout the state, usually in spring (while flowering), but plants may be found throughout the year. It is a native of Europe now widely naturalized.

Disturbed ground, roadsides, fields, pastures.