The "Sakura-so" (Primula sieboldii) belongs to Primulaceae (the Primrose family). It is a perennial herb that is distributed throughout Japan, as well as the Korean Peninsula, north-eastern China and eastern Siberia. This herb grows in wet places of mountains or along streams and can reach 20-30 cm in height. The leaves are basal and long petiolated with wrinkled surfaces. The umbel is borne on the stalk and the magenta to white flowers bloom from April to May. It is a typical species in Japanese Primula genus. In Chinese, it is called "櫻草" (ying cao).