クルミ科サワグルミ属の落葉高木で、学名は Pterocarya rhoifolia。英名は Japanese wingnut。
The Japanese wingnut (Pterocarya rhoifolia) belongs to Juglandaceae (the Walnut family). It is a tall deciduous tree that is distributed southward from southern Hokkaido to Honshu, Shikoku and Kyushu in Japan. This tree grows in montane screes along streams and can reach 10-20 m in height. The leaves are alternate and odd-pinnate compound with 5-10 pairs of oblong leaflets. The male and female clusters are borne and drooping from April to June. The fruits are nuts with winged. The timber is soft and used for making tubs, Japanese wooden footgears and kyogis (paper-thin sheet of wood).