Trees to 20 m tall. Bark smooth; branches nearly 4-angled. Leaves in whorls of 3 or 4; petiole 1-4 cm; leaf blade narrowly obovate or narrowly elliptic, 10-53 X 4-19 cm, leathery, pubescent abaxially, apex usually acuminate; lateral veins 16-33 pairs, at 60-70° to midvein. Cymes terminal, 3-branched, 5-9 together, pubescent; peduncle 4-6 cm. Pedicel 4-5 mm. Corolla tube slightly longer than lobes, 4.5-6 mm; lobes overlapping to right, ciliate; disc absent. Ovaries distinct, glabrous. Follicles linear, to 61 cm X 2-5 mm. Seeds pubescent, ends with deltoid wings, with long stiff hairs all around. Fl. Oct-Nov. 2n = 22.

Cultivated for medicine.

S Guangdong, S Yunnan [Indonesia, Malaysia, Philippines, Thailand, Vietnam].