Description from Flora of China
Trees to 30 m tall; trunk to 1 m d.b.h. Bark grayish black to gray, coarsely split and thick. Branchlets conspicuously white or yellowish long lenticellate, glabrous, or tomentose or appressed villous at least when young, hairs tawny, rarely silvery. Leaves alternate or subopposite, spaced along branchlets; petiole 1-3 cm, moderately stout, with 2(-4) glands 1-5 mm below apex; leaf blade elliptic, 7-18 × 4.5-10 cm, both surfaces glabrous, or appressed (and rarely silvery) villous at least when young, base obtuse-rounded or cuneate, oblique, apex mucronate; lateral veins in 6-12 pairs. Inflorescences axillary or terminal, simple spikes, 5-10 cm, numerous flowered, sometimes grouped at branchlet apex and forming a panicle; axis glabrous or sparsely hairy, with denser hairs near base of flowers. Flowers slightly fragrant, bisexual. Calyx tube distally cupular, 2.5-3.5 mm, abaxially glabrous, adaxially tawny tomentose; lobes 5, apex mucronate to aristate. Stamens 10, exserted, 3-4 mm. Fruit not stipitate, blackish brown when ripe, ovoid or broadly so, ellipsoid, or cylindric-ovoid, obtusely 5-ridged, 2-4.5 × 1.2-2.5 cm, rigid, becoming deeply wrinkled when dry, glabrous. Fl. May-Jun, Sep, fr. Jul-Dec. 2n = 24, 48, 72.
The fruit yields a black dye used to dye cloth, at least in Guangdong.
Sparse forests, secondary bamboo forests, sunny forest margins, thickets, also cultivated on village commons; below 500 to 1800 m. Native in W Yunnan; cultivated in Fujian, Guangdong, Guangxi (Nanning), and Taiwan (Nantou) [Bangladesh, Bhutan, Cambodia, India, Laos, Malaysia (introduced), Myanmar, Nepal, Sri Lanka, Thailand, Vietnam].