The Ku shen (Sophora flavescens) belongs to Fabaceae (the Pea family). It is a perennial herb that is native from Honshu south to Shikoku and Kyushu, as well as the Korean Peninsula, China and Siberia. This herb grows in montane grasslands or dry riverbeds, and it can reach 1-1.5 m in height. The leaves are impari-pinnate compound. The flowers are "Itachi-sasage (Lathyrus davidii)"-like, pale yellow, and bloom in the long racemes from June to July. The swollen roots are called "Ku shen" and used as a Chinese medicine for anti-itch drug or anthelminthic. The Japanese name is derived from the strong bitter like a lightheaded sensation.