Description from Flora of China
Piper mekongense C. de Candolle.
Subshrubs erect, to more than 1 m high, glabrous except for a few hairs at bases of flowers, dioecious. Stems black when dry; nodes prominent. Petiole ca. 1 cm; prophyll ca. 2/3 as long as petiole; leaf blade elliptic or broadly elliptic, 11-19 × 4-9 cm, papery, glandular, often ± reddish adaxially when dry, base shortly tapered or subcuneate, rarely rounded, usually symmetric, apex shortly acuminate and mucronate; veins 5-7, apical pair arising 2.5-5 cm above base, alternate, reaching leaf apex, others ± basal; reticulate veins prominent, transversely oblong. Spikes leaf-opposed. Male spikes 7-9 cm × ca. 2 mm; peduncle slightly longer than petioles; bracts obovate-oblong, ca. 1.8 × 0.7 mm, adnate to rachis, margin and apex free. Stamens 3; filaments ca. as long as anthers, sometimes much longer; anthers ovoid. Female spikes 7-11 cm, to 17 cm in fruit; peduncle and rachis as in male spikes; bracts oblong, 3.5-4 × 1.1-1.3 mm. Ovary ovoid, distinct; stigmas 3 or 4, ovate, apex acuminate. Drupe drying black, ovoid, 3-3.5 mm in diam., tuberculate, apex ± subacute, sessile. Fl. Apr-Jun.
Wet places within forests; 800-1400 m. SW Guizhou, S Yunnan [Laos]