Sonchus oleracea typically has grey-green leaves with few (soft) prickly tips, while the leaves of Sonchus asper are typically glossy green with many (soft) prickly tips, but can sometimes be blue-green. In difficult cases the fruits provide unquestionable identification attributes: The achenes of Sonchus asper are more bulbous than the more elongated ones of Sonchus oleraceus. Beneath the longitudinal furrows which are availabe at both, the achenes of Sonchus oleraceus have usually a transversely wrinkled surface, which is not present on the achenes of Sonchus asper with smooth surface.