White sweet clover (Melilotus alba) belongs to the Fabaceae (the Pea family). It is a biennial herb that is native to Central Asia and Europe. It was introduced into Japan in the last days of Edo Era (about 150 years ago), and nowadays it can be found everywhere. It was also introduced into North America as a meadow grass, and it is naturalized widely except circumpolar area. This herb can reach 90-240 cm in height. The leaves are trifoliate. The racemes are borne on the axils, and the small, white, papilionacenous flowers bloom from June to August. Its characteristic sweet odour, intensified by drying, is derived from coumarin.