The Prickly sow thistle (Sonchus asper) belongs to Asteraceae (the Aster family). It is a biennial herb that is native to Europe. This herb was introduced into Japan in Meiji Era (1868-1912). It grows in roadsides or waste places and can reach 50-100 cm in height. It passes the winter by radical leaves and extends midair stem in spring. The leaves enfold stems, and have prickly-pointed toothed edges. The yellow ray flowers come in March to October.