Vines woody. Stems to 10 m; branches subterete, indistinctly 10-grooved, glabrous. Leaves ternate; petiole 2.4--4 cm; leaflet blade ovate or narrowly so, 3.5--7 × 1.8--3 cm, papery, abaxially sparsely appressed puberulous, adaxially very sparsely puberlous on veins, base rounded, margin dentate, apex acuminate or long acuminate; basal veins nearly flat. Flowers usually 2, borne with leaves from axillary buds of old branches, 6.5--7 cm in diam.; pedicel 9--11 cm, very sparsely puberulous. Sepals 4, white, spreading, ovate-oblong, 3.3--3.7 × 1.1--1.6 cm, abaxially subglabrous, adaxially glabrous, margin velutinous, apex attenuate and shortly cuspidate. Stamens 7--14 mm, glabrous; anthers linear or narrowly oblong, 2.5--3 mm, apex obtuse. Ovaries glabrous; style 8--11 mm, densely villous. Fl. May.

* Forests, bamboo thickets on slopes; 2400--2700 m. SE Yunnan (Wenshan Xian).