Description from Flora of China
Hydrangea bretschneideri var. glabrescens Rehder; H. xanthoneura Diels var. glabrescens (Rehder) Rehder.
Shrubs 1-3(-5) m tall. First year's branchlets red-brown to brown, long pilose, glabrescent. Second year's branchlets lighter in color, without lenticels; bark thin, peeled off into fragments. Petiole 1-3.5 cm, pilose; leaf blade ovate, ovate-oblong, obovate-oblong, or elliptic-oblong, 7-16 × 2.5-7 cm, papery, abaxially densely gray-white crisped to suberect villous, glabrescent, adaxially glabrous except shortly pilose along veins, secondary veins 7 or 8 on both sides of midvein, erect and obliquely ascending, abaxially slightly prominent, base broadly cuneate to subrounded, margin serrate, apex acuminate. Inflorescences corymbose cymes, 8-15 cm wide, apex truncate to slightly arcuate; branches 3, slightly unequal with central one usually shorter than others, densely pubescent. Sterile flowers with sepals 4, elliptic, ovate, obovate, or suborbicular, 1.3-1.7 × 1-1.6 cm, margin entire. Fertile flowers with calyx tube cupular, ca. 1 mm; teeth triangular, 1-1.5 mm. Petals white, ovate-lanceolate to oblong, 2.5-3 mm. Stamens 10, unequal; anthers subglobose, 0.5-0.6 mm. Ovary less than 1/2 superior. Styles 3, 1-1.5 mm in fruit. Capsule ovoid-globose, 3-3.5 mm in diam., projected apical part conical, ca. 1.5 mm, slightly shorter than calyx tube. Seeds brownish, narrowly ellipsoid, winged at both ends; wings 0.5-0.6 mm; seed coat striate veined. Fl. Jun-Jul, fr. Sep-Oct.
* Dense to sparse forests along stream banks in valleys or on mountain slopes; 1200-2800 m. Gansu, Hebei, Henan, Ningxia, Qinghai, Shaanxi, Shanxi.