Description from Flora of China
Rhododendron hangzhouense W. P. Fang & M. Y. He; R. sanidodeum P. C. Tam.
Shrubs, 2–3(–8) m tall; young shoots gray-brown pubescent and sparsely glandular-setose. Petiole ca. 5 mm, pubescent and glandular-hairy; leaf blade subleathery, ovate or ovate-elliptic, 3–5.5 × 1.5–2.5 cm; base broadly cuneate or subrounded; margin finely undulate-crenate; both surfaces glabrous except for the pubescent midrib abaxially. Inflorescence subapical, 1-flowered. Pedicel 1.2–1.6 cm, pubescent and glandular-hairy; calyx deeply lobed; lobes ovate or obovate, 3–5 × 3–4 mm, puberulent abaxially or glandular-hairy, margin with dense short glandular hairs, apex obtuse and fluted; corolla rotate, purple or purplish, with dark red flecks on upper three lobes, 1.8–2.1 cm; lobes broadly obovate, ca. 1.4 cm wide, pubescent near the base within; stamens 5, unequal, 2–2.8 cm, as long as or slightly shorter than corolla; filaments flat, puberulent below the middle; ovary densely shortly glandular-hairy; style 2.5–3.2 cm, slightly curved, exserted, longer than stamens, glabrous. Capsule ovoid, ca. 7 × 6 mm, densely shortly glandular-hairy. Fl. Apr–May, fr. Jun–Oct.
The characters used to separate Rhododendron bachii from R. ovatum are fairly trivial, especially those relating to the calyx indumentum. Furthermore, there is continuous variation in these characters, suggesting that R. bachii should be treated as a synonym of R. ovatum.
Open forests; 600–1600 m. Anhui, Guangdong, Guangxi, Guizhou, Hubei, Hunan, Jiangxi, Sichuan, Zhejiang.