皋月杜鹃 gao yue du juan

Azalea indica Linnaeus, Sp. Pl. 1: 150. 1753; A. macrantha Bunge; Rhododendron breynii Planchon; R. danielsianum Planchon; R. decumbens D. Don ex G. Don; R. hannoense Nakai; R. lateritium Planchon; R. macranthum (Bunge) G. Don (1834), not Griffith (1848).

Shrubs, semievergreen, 1–2 m tall; branches many; young shoots densely red-brown strigose, glabrescent. Summer and winter leaves different. Petiole 2–4 mm, coarsely red-brown strigose; leaf blade papery, narrowly lanceolate or oblanceolate, 1.7–3.2(–4.5) × ca. 0.6 cm; base narrowly cuneate; margin sparsely and finely crenate-serrate; apex obtusely pointed; abaxial surface sparsely red-brown strigose; adaxial surface shiny-strigose. Inflorescence 1–3-flowered. Pedicel 0.6–1.2 cm, coarsely white strigose; calyx lobes elliptic-ovate or suborbicular, pale green, 2–3 × 1.5–2 mm, softly white-hairy; corolla broadly funnelform, bright red, occasionally rose-red, with dark red flecks, 3–4 × 3.7(–6) cm; tube ca. 13 mm, lobes broadly elliptic, 1.7–2 × ca. 1.6 cm; stamens 5, unequal, 1.6–2.2 cm, shorter than corolla, filaments puberulent at base; ovary ca. 3 mm, densely shiny brown strigose; style 2.3(–4.5) cm, longer than stamens, glabrous. Capsule oblong-ovoid, 6–8 mm, densely red-brown strigose. Fl. May–Jun.

Widely cultivated in China [native to Japan].