Description from Flora of China
Vincetoxicum stenophyllum (Hemsley) Kuntze.
Roots fascicled. Stems erect, to 40 cm, pubescent along 1 side. Petiole ca. 2 mm; leaf blade linear-lanceolate, ca. 6 cm × 5 mm. Inflorescences umbel-like, 2-2.5 cm, sometimes 2 separated by a short rachis; peduncle 0.5-1(-1.7) cm. Sepals ovate, ca. 1.3 × 0.7 mm. Buds ca. 3 mm. Corolla deep purple, white, or pale yellow, rotate; tube short; lobes ovate, obtuse, villous inside. Corona shallowly cupular; lobes fleshy, ovate, thick, pouched, apex rounded, each lobe adnate ventrally to anther and dorsally to corolla. Pollinia oblong; stigma head slightly convex. Follicles linear-lanceolate in outline, ca. 4 cm × 5 mm. Seeds oblong-ovate, ca. 7 × 3 mm; coma ca. 2 cm. Fl. May.
* Moist lowlands. Guizhou, Hubei, Sichuan.