Description from Flora of China
Hydrangea macrophylla (Thunberg) Seringe subsp. chungii (Rehder) E. M. McClintock.
Shrubs small, 0.3-0.7 m tall. Branchlets densely spreading, terete, translucent roughly villous when young, glabrescent; bark pale, easily peeled off. Petiole thick, 1-4 cm; leaf blade elliptic to oblong-elliptic, 12-20 × 4.5-8.5 cm, membranous, both surfaces densely roughly villous, abaxially more densely so, secondary veins 8-10 on both sides of midvein, slightly prominent on both surfaces, base narrowly to broadly cuneate, margin roughly serrate, apex acuminate. Inflorescences corymbose cymes, 11-15 cm wide, densely roughly villous; peduncle short; branches 3, subequal. Sterile flowers with sepals 3 or 4, suborbicular to broadly orbicular, 1.5-1.7 × 1.5-2 cm in fruit, apex rounded to emarginate. Fertile flowers with calyx tube ca. 1.5 mm, pubescent; teeth triangular, ca. 1 mm. Petals blue-purple, elliptic, ca. 2 mm in bud. Stamens 10, subequal. Ovary less than 1/2 superior. Styles 3 or 4, spreading, 1-1.5 mm in fruit; stigmas subcapitate to nearly hemispheric. Capsule subglobose, 2.5-3 mm in diam., projected apical part 0.7-1 mm, shorter than calyx tube. Seeds brown, broadly obovoid to broadly ellipsoid, 0.3-0.4 mm, wingless or sometimes shortly winged at both ends; seed coat net veined. Fl. Jun-Jul, fr. Sep-Oct.
* Dense forests or thickets on mountain slopes or on trailsides; 200-800 m. NW Fujian.