Description from Flora of China
Hydrangea angustipetala Hayata var. subumbellata W. T. Wang; H. linkweiensis var. subumbellata (W. T. Wang) C. F. Wei.
Shrubs to 3 m tall. Branchlets dark purple-brown, sparsely pubescent when young, glabrescent; bark peeled off into irregular fragments. Petiole 4-10 mm, densely villous; leaf blade dark red-brown on both surfaces or lighter abaxially when dry, lanceolate to ovate-lanceolate, slightly asymmetric, 5-14 × 1.7-4 cm, thinly papery, abaxially glabrous or sparsely puberulent with hairs denser along veins, adaxially glabrous or subglabrous, base broadly cuneate to obtuse, margin sparsely denticulate to serrate, apex caudate-acuminate to falcate acuminate. Inflorescences corymbose cymes, apex truncate; peduncle 3-5 cm; branches 3, unequal with central one shorter and lateral ones longer, 5-8 cm, spreading and appressed pubescent. Sterile flowers with sepals 3, triangular-ovate to broadly ovate, unequal, 1.5-2.5 × 1.5-2.7 cm in fruit, margin entire. Fertile flowers with calyx tube cupular, ca. 1 × 1.5 mm, slightly pilose; teeth ovate-lanceolate, 1.5-2.5 mm. Petals yellow, oblanceolate to oblong-obovate, 3.5 × 1.2-1.7 mm, with l midvein, base with a claw ca. 0.5 mm. Stamens subequal; anthers oblong, 1-1.2 mm. Ovary ca. 1/2 superior. Styles 3 or 4, slightly spreading, 1.5-2 mm in fruit; stigmas enlarged, decurrent along style adaxially. Capsule ovoid to ellipsoid, 3-4.5 × 2.3-4 mm, projected apical part ca. 1.5 mm, equaling calyx tube. Seeds brown, oblong, obovoid, or subglobose, ca. 0.6 × 0.3-0.5 mm, wingless; seed coat net veined. Fl. May-Jun, fr. Aug-Oct.
* Dense to sparse forests or thickets on mountain slopes or in valleys; 700-1100 m. E Guangxi, SW Hubei.