The "Yama-narashi" (Populus sieboldii) belongs to Salicaceae (the Willow family). It is a tall deciduous tree that is an endemic species and distributed throughout Japan. This tree resembles to the Japanese poplar (Populus suaveolens), and grows mainly in arid places and up to a height of about 20 m. The leaves are broad elliptic and grayish white beneath. They have long petioles, sway greatly and rustle when the wind blows. The clusters, around 5-10 cm are descending and flowers will bloom around March. It is dioecious. It is also called "Hakoyagi" in another name, but it depends on the box being made of this material.