Herbs perennial. Roots fleshy, long, much branched. Stems reddish, to 4 m, narrowly 3-5-winged, ± angular, gla-brous or densely pilose-tomentose on young parts. Petiole 2-10 cm, often winged; leaf blade cordate-circular, ovate, broadly ovate, ovate-lanceolate, or lanceolate, 4-14 X 3.5-14 cm, abaxially pubescent, adaxially appressed pilose to gla-brous, base cordate, truncate or obtuse, margin entire or undulate, apex acute or acuminate, mucronulate. Inflorescences cymose, often 2-flowered; peduncles 0.5-3 cm, usually terete; bracts 2, oblong to ovate-oblong, 1-2.5 cm, concave, pubescent. Pedicel 1.5-2 cm, striate-angular, clavate, to 4 cm in fruit. Sepals ovate to broadly ovate, unequal; outer 2 sepals 1.5-2 cm, abaxially pubescent; inner 3 shorter, subglabrous. Corolla white, sometimes with a yellowish base inside, broadly funnelform, 3.5-4 cm, glabrous, minutely yellowish glandular outside; limb 5-lobed. Filaments pubescent basally; anthers twisted. Fruit enclosed in cupular calyx, depressed globose, ca. 1.5 cm in diam. Seeds dull black, ovoid-trigonous, ca. 6 mm, glabrous. 2n = 30..