Trees to 30 m. Branchlets 4-angled, glabrous. Leaves 25-35(-40) cm; petiole 6-8 cm; axis with ridges sometimes subalate, leaflet joint brown curly hairy; leaflets 7-11(-13), subsessile; leaflet blade oblong to ovate-oblong, 5-20 × 2-5 cm, papery, adaxially glabrous or sparsely white hirsute, abaxially curly hairy along veins, especially denser at base of midrib, base cuneate to blunt, slightly oblique, margin serrulate, apex acuminate or caudate; primary veins 8-11 on each side of midrib. Panicles lateral at branches of previous year, 15-20 cm; staminate panicles congested; bisexual ones somewhat lax. Pedicel 3-5 mm in staminate panicles, longer in bisexual. Flowers polygamodioecious, appearing before leaves, without calyx and corolla. Samara oblong to obovate-lanceolate, 3-3.5(-4) cm × 6-9 mm; wing decurrent to middle or base of nutlet, obviously twisted. Fl. Apr-Jun, fr. Aug-Sep.
Sparse woods and in open river valleys, on gently sloping hills and on rich soils ; at elevations from 700-2,100 metres.
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