Japan Flora: Tall tree with gray-brown smooth bark and much divided slender branches, the branchlets brownish red, puberulent, the lateral ones deciduous in autumn; leaves membranous, narrowly ovate or narrowly ovate-oblong, 3-7 cm. long (sometimes to 12 cm. long in young vigorous shoots), 1-2.5 (-5) cm. wide, long-acuminate, shallowly cordate to rounded at base, slightly scabrous or nearly smooth and dull above, young, the petioles 1-3 mm. long, puberulous on upper side; fruit sessile, nerved, about 5 mm. across, obliquely ovate- orbicular, glabrous. Apr.-May. Lowlands and mountains;

Honshu, Shikoku, Kyushu; frequently planted around houses. Korea, China, and perhaps Formosa.

var. stipulacea Makino. Leaves pilose on both surfaces. Honshu.

Korea Flora: Deciduous tree. Height 26m. Diameter 3m. Branches divergent. Bark smooth for long periods, exfoliating in scales, with horizontally elongated lenticels. Winter buds ovoid to conical, apex acute, with 8-10 scales; terminal buds equal to or slightly larger than lateral buds (2-4mm long). Branchlets slender with fine pubescence when young. Leaf scars semicircular. Leaves alternate, oblong-elliptical, elliptical, or ovate, apex acuminate, base cuneate, size 2-7(13)cm × 1-2.5(5)cm. Leaves highly variable in size from small to very large. Margin with simple serration, both surfaces becoming glabrous; lateral veins 8-14 pairs. Petiole 15mm long. Flowers monoecious; staminate flowers clustered at base of new shoots with (4)-6 divided petals and (4)-6 stamens; pistillate flowers solitary on upper portion of new shoots, with reduced stamens and bifurcated style. Fruit and seeds asymmetrically circular, 4mm in diameter, with ridge on dorsal surface.

Sporophyte chromosome number: 28.
Flowering period: Early April-Early May
Fruiting period: Mid-MayDistribution: Central and southern China, Japan (Honshu-Kyushu); Hwanghae-do, Gyeonggi-do, Chungcheongbuk-do, Gyeongsangbuk-do, and Jeollabuk-do

Ecological characteristics: Light-demanding species that grows poorly under other trees when young. Thrives in areas with abundant light, deep soil, and high moisture content. Well-adapted to valleys or lower mountain slopes near streams and valleys. Strong resistance to cold and snow but weak against pollution, showing severe abnormal defoliation in urban areas. Typical lifespan exceeds 300 years, growing into large trees. Very strong sprouting ability. Seeds produced abundantly every 2-3 years.