Description from Flora of China
Hydrangea coenobialis var. acutidens Chun; H. stenophylla Merrill & Chun var. decorticata Chun.
Shrubs 1-3 m tall. Branches purple-red to dark purple-red, terete, thick, glabrous; bark peeled off into fragments when old. Petiole thick, 1-2 cm, glabrous; leaf blade abaxially greenish, adaxially dark green, ovate-lanceolate, lanceolate, or elliptic, 9-20 × 2.5-5 cm, papery to thickly so, abaxially sparsely appressed puberulous, adaxially glabrous, secondary veins 8-11 on both sides of midvein, abaxially elevated, base obtuse to broadly cuneate, margin serrulate to long sharply serrate, apex acuminate to caudate-acuminate. Inflorescences corymbose cymes, 7-12 cm wide, apex truncate to slightly arcuate; branches 3, thick, densely pubescent. Sterile flowers absent. Fertile flowers with calyx tube funnelform, ca. 1.5 × 2 mm; teeth ovate to ovate-triangular, ca. 1 mm. Petals yellowish, oblanceolate to obovate-oblanceolate, 2.5-4 × 1-1.2 mm. Stamens 8, subequal, ca. 3 mm; anthers oblong, 1-1.5 mm. Ovary ca. 1/2 superior. Styles 3, erect or slightly spreading, ca. 2 mm in fruit; stigmas hemispheric, enlarged. Capsule cupular, 3.5-4 mm in diam., projected apical part 2-2.5 mm, subequaling calyx tube; pedicel 0.6-1.4 cm. Seeds brownish, obovoid to subglobose, ca. 0.5 × 0.4-0.5 mm, wingless; seed coat net veined. Fl. May, fr. Sep.
* Stream banks in dense to sparse valley forests, trailsides on mountain slopes; 200-800 m. NC Guangdong, E Guangxi.