The sweet woodruff (Asperula odorata) belongs to Rubiaceae (the Madder family). It is a perennial herb that is distributed widely, Hokkaido and Honshu in Japan, as well as Asia, Europe and North Africa. This herb grows in mountain forests, and can reach 20-30 cm in height. The stems are not brranched, and they bear 2 oblong leaves and 4-8 stipulars in dense false whorls. The white funnel-shaped flowers bloom in the terminal cymes from May to July. The corolla is four-lobate. The dried plants have a flavor of coumarin odor, and used as a flavouring in drinks.