Similar species include Smooth Sow-thistle ( S. oleraceus ), Perennial Sow-thistle ( S.arvensis) Annual spreading by seed which have short plumes of silvery green hairs . Flowers June - October , Flowers Bright yellow
Sonchus asper is a creeping rooted annual, growing 0.4 to 1.5 m (11/3 - 5 ft) tall. Its stems branch near the top, while its leaves, which have weak marginal prickles, clasp the stem. Plants contain a bitter milky juice. Flowers are golden-yellow, up to 25 mm (1 in) broad.