Climbers woody, glabrous except for rachis and bracts, dioecious. Stems ridged, rooting at nodes. Petiole 0.4-2 cm, shorter in leaves toward apex of stem, prophylls ca. 1/2 as long as petiole; leaf blades toward base of stem ovate, 8.5-11 × 6-7 cm, papery, without evident glands, base usually cordate, symmetric, apex acute; veins 5(-7), all ± basal; reticulate veins conspicuous, transversely oblong toward apex; leaf blades toward apex of stem narrowly ovate, 6-11 × 1.5-4.5 cm, base usually oblique, rounded or slightly tapered, apex acuminate. Spikes leaf-opposed. Male spikes white, 3-6.5 cm × ca. 2 mm; peduncle 1-1.8 cm; rachis and undersides of bracts densely white pubescent; bracts orbicular, ca. 1 mm wide, peltate, sessile. Stamens 2; filaments nearly as long as anthers. Female spikes white, 1-1.5 cm × ca. 3 mm; peduncle nearly as long as rachis; bracts as in male spikes. Ovary partly immersed in rachis; stigmas 3 or 4, tomentose. Drupe globose, ca. 2 mm in diam., partly immersed in rachis. Fl. Apr-Jun.

Material of this species lacking fruit has often been confused with Piper hancei. However, P. austrosinense can be easily distinguished by its white flowers, whereas P. hancei has yellow flowers.

* Forests, on trees or rocks; 200-600 m. E and SW Guangdong, SE Guangxi, Hainan