Plants polygamo-dioecious. Branchlets terete, slender, with longitudinal ridges, sparsely pubescent when young, then subglabrate; tendrils unbranched, leaf-opposed. Leaves simple, 3-5-lobed to -cleft; stipules brownish, lanceolate, 2-3 × 1-1.5 mm, pubescent, entire, apex obtuse; petiole 4-6 cm, pubescent; leaf blade abaxially purplish, adaxially purplish when young, becoming purplish green when old, ovate or ovate-lanceolate, 7-12 × 5-7 cm, abaxially pubescent on veins, adaxially pubescent on veins, basal veins 5, lateral veins 5 or 6 pairs, veinlets usually raised, base cordate, notch obtuse, rarely acute, base of midlobes broad, rarely constricted, margin irregularly 12-16-toothed on each side, teeth sharp, apex acute or acuminate. Panicle leaf-opposed, 6-8 cm, basal branches poorly developed; peduncle 1-2 cm, pubescent. Pedicel 2-3 mm, subglabrate. Buds obovoid, 1.5-2 mm, apex rounded. Calyx ca. 2 mm, entire. Filaments filiform, ca. 0.8 mm; anthers yellow, elliptic, ca. 0.4 mm.