Trees 10-20 m tall, subglabrous. Branchlets terete, scabrous. Leaves in whorls of 3 at branch tips; petiole 4-5 cm; axis adaxially with ridges expanding into narrow wings; leaflets 7-11(-13); petiolule 5-12 mm; leaflet blade ovate, lanceolate, or narrowly lanceolate, 2.5-8(-12) X 1.5-4 cm, papery, adaxially glabrous, abaxially with dense minute glandular dots, sometimes puberulent along midvein, base cuneate, attenuate to petiolule, margin irregularly deltate dentate, apex acuminate or long acuminate; primary veins 10-14 on each side of midvein. Cymose panicles lateral at branches of previous year, ca. 5 cm. Flowers polygamous, appearing before leaves, opposite or in whorls of 3; without calyx and corolla. Samara oblanceolate, 3-5 cm X 5-8 mm; wing decurrent to base of nutlet, strongly twisted. Fl. Apr-Jun, fr. Jul-Oct. 2n = 46.