The "Bakko-yanagi" (Salix bakko) belongs to Salicaceae (the Willow family). It is a tall deciduous tree that is distributed to Shikoku and northward from Kinki district of Honshu to southwestern Hokkaido. This tree grwos in sunny mountains or moors and can reach 5-15 m in height. The barks are dark gray and nearly smooth. The leaves are alternate and covered with woolly hairs on the abaxial sides. The catkins are borne and bloom flowers from March to April before foliation. The Japanese name comes from the regional name in the Tohoku region.