Shrubs climbing, somewhat herbaceous. Stems terete, striate, villous, glabrescent. Petiole 1.5-6 cm, densely villous; leaf blade ovate to ovate-lanceolate, obovate-oblong, or linear, 3-18 × 0.3-8 cm, papery, abaxially sparsely white villous, adaxially glabrous, veins palmate, 2-4 pairs from base, base shallowly cordate to auriculate, sinus 0.5-1 cm deep, margin lobed or entire, apex acute to acuminate. Flowers axillary, solitary or paired. Peduncle usually pendulous, 2-7 cm, pubescent; bractlets brownish, ovate to lanceolate or subrotund, 5-15 × 3-15 mm, inserted at base or middle of peduncle, with short stalk or sessile and amplexicaul. Calyx yellow-green with purple veins, throat yellow, 3-4 cm; tube horseshoe-shaped, abaxially villous; basal portion of tube 20-25 × 30-80 mm; limb discoid-subrotund, 2-3 cm in diam., 3-lobed; lobes broadly ovate. Anthers oblong, ca. 1 mm. Gynostemium 3-lobed. Capsule cylindric or ovoid, 3-7 × 1.5-2 cm, dehiscing basipetally. Seeds obovoid, 3-4 × 2-3 mm. Fl. Mar-May, fr. Jun-Aug.