Description from Flora of China
Trees, to 20 m tall; crown conical. Trunk conspicuous. Twigs purple-brown to brown-gray, with round convex lenticels, stellate tomentose, glabrescent. Petiole to 11 cm; leaf blade ovate to ovate-cordate, to 20 cm or longer, abaxially moderately to densely tomentose or subglabrous, adaxially sparsely pubescent, hairs short branched and stalked, margin entire or undulate, apex narrowly acuminate and apiculate. Thyrses broadly conical, to 1 m; cymes sessile or subsessile, 3-5-flowered. Pedicel less than 1 cm. Calyx obconical, to 2 cm, stellate tomentose; lobes to 1/2 of calyx length. Corolla white with purple striations to wholly purple, subcampanulate, 5.5-7.5 cm, glandular pubescent. Stamens 2-2.5 cm. Ovary glandular. Style ca. 3 cm. Capsule ellipsoid to ovoid-ellipsoid, 3-4 cm, viscid glandular when young; pericarp thin; persistent calyx adnate or spreading, often not reflexed. Seeds oblong, 5-6 mm including wing. Fl. Apr-May, fr. Aug-Sep.
Wild or cultivated. Forests, mountain slopes; 1200-3000 m. Guizhou, Hubei, Hunan, Sichuan, Yunnan [Vietnam].