Description from Flora of China
Hydrangea macrophylla (Thunberg) Seringe subsp. stylosa (J. D. Hooker & Thomson) E. M. McClintock; H. taronensis Handel-Mazzetti.
Shrubs ca. 1.5 m tall. First year's branchlets sparsely pubescent. Second year's branchlets gray-white. Petiole 1.5-3 cm, brownish pubescent; leaf blade elliptic, 6-14 × 3-7 cm, papery, both surfaces glabrous or midvein crisped pubescent, secondary veins 6-8 on both sides of midvein, abaxially slightly prominent, base cuneate to subrounded, margin serrate, apex shortly acuminate. Inflorescences corymbose cymes, 5-10 cm wide, apex truncate; peduncle 3-7 cm; branches 3, subequal, brownish pubescent. Sterile flowers with sepals 3 or 4, broadly ovate to broadly elliptic, unequal, 0.5-2 cm, margin few denticulate. Fertile flowers with calyx tube campanulate; teeth ovate to suborbicular, 1-1.5 mm, apex obtuse. Petals reflexed after flowering, blue, oblong, slightly unequal, 2.5-3.5 mm. Stamens 10, subequal, longer ones longer than petals; anthers blue, oblong, ca. 1 mm. Ovary ca. 1/3 superior. Styles 3-5, spreading, slender, 2.5-3 mm in fruit; stigmas capitate, small. Capsule subglobose, ca. 2.7 mm in diam., projected apical part ca. 1 mm, ca. 1/3 as long as capsule body. Seeds brown, ellipsoid to oblong, 0.5-0.8 mm, shortly winged at one or both ends; seed coat net veined. Fl. Jun-Jul, fr. Sep-Oct.
Dense forests; 2700-3000 m. W Yunnan [Bhutan, Myanmar, Sikkim].