Description from Flora of China
Hydrangea heteromalla var. parviflora C. Marquand & Airy Shaw; H. khasiana J. D. Hooker & Thomson; H. mandarinorum Diels; H. vestita Wallich.
Shrubs or small trees, 2-5 m tall or more. Branchlets red-brown to brownish, pubescent, glabrescent, with a few elliptic lenticels. Petiole purplish red, 2-4 cm, pilose; leaf blade elliptic, broadly ovate, or oblong-ovate, 6-15 × 3-8 cm, papery or at base of inflorescence membranous, abaxially densely gray-white velutinous, adaxially yellow-brown strigose to subglabrous, secondary veins 7-9 on both sides of midvein, base shallowly cordate, obtuse, or truncate, margin densely serrulate or doubly serrate, apex acute to acuminate. Inflorescences corymbose cymes, 15-20 cm wide, to 27 cm wide in fruit, apex arcuate; peduncle present; branches 3, pubescent; bracts and bracteoles lanceolate to linear. Sterile flowers with sepals 4, white or yellowish, elliptic, broadly ovate, or broadly orbicular, 0.7-1.6 × 0.5-1.4 cm, base rounded to shallowly cordate, margin entire. Fertile flowers with calyx tube nearly funnelform to campanulate, 1-1.5 mm; teeth triangular, 0.5-1.5 mm. Petals white or yellowish, oblong-ovate, 1.8-2 mm. Stamens 10, unequal; anthers subglobose, ca. 0.6 mm. Ovary up to 1/2 superior. Styles 3 or 4, erect, subulate, 1-1.3 mm in fruit; stigmas small. Capsule ovoid-globose to subglobose, 2.5-3.5 mm in diam., projected apical part conical, 0.8-1.2 mm, ca. 1/3 as long as capsule body. Seeds yellow-brown, ellipsoid to oblong, slightly compressed, 0.7-1 mm, winged at both ends; wings 0.2-0.5 mm; seed coat striate veined. Fl. Jun-Jul, fr. Sep-Oct.
Hydrangea heteromalla forms a species complex out of which a number of segregate species have been recognized. One of the present authors (Bartholomew) feels that species nos. 18-23 below all fall within the pattern of variation found in H. heteromalla, in the synonymy of which they would be better treated.
Forests or thickets on mountain slopes or tops; 2400-3400 m. Sichuan, S Xizang, Yunnan [Bhutan, NE India, Nepal, Sikkim].