Ohwi 1985 Flora of Japan

Japan Flora: Dioecious tree with glabrous branches; leaves thin, ovate- oblong, 8-15 cm. long, 3.5-7 cin. wide, acuminate, cordate or shallowly so at base, regularly and sharply double-serrate, short-pubescent, often with long persistent appressed hairs on nerves beneath, the 18-23 pairs of lateral nerves ascending-parallel, the petioles 1-1.5 cm. long; inflorescence nearly glabrous, racemose, pendulous, loosely few to rather many-flowered, 5-8 cm. long, on short peduncles, the pedicels 1-2.5 cm. long in fruit; flowers pale green, 1-1.2 cm. across; sepals 4, narrowly elliptic, long-pubescent, 5-6 mm. long; petals in pistillate flowers narrowly ovate, about as long as the sepals, often absent in staminate flowers; stamens 5-6; samaras soon glabrous, ascending, 2.5-3 cm. long inclusive of the wing. Valleys and ravines in mountains;

Hokkaido, Honshu, Shikoku, Kyushu; common.