424. Rhododendron citriniflorum I. B. Balfour & Forrest, Notes Roy. Bot. Gard. Edinburgh. 11: 35. 1919.
橙黄杜鹃 cheng huang du juan
Dwarf shrubs, 0.6–1.2 m tall; bark gray-brown, smooth, usually falling off in flakes; young shoots glabrous; bud scales persistent. Petiole flat, usually winged, 5–10 mm, white-tomentose when young; leaf blade leathery, oblong-obovate, 2.5–6 × 1.5–2 cm; base cuneate; margin revolute; apex obtuse, rounded, apiculate; abaxial surface densely gray-brown tomentose, hairs dendroid; adaxial surface green, glabrous; midrib grooved adaxially; lateral veins 8-paired, impressed. Inflorescence umbellate, 2–6-flowered; rachis ca. 3 mm, tomentose and glandular. Pedicel 1–2.6 cm, eglandular to densely glandular-setose; calyx 2–12 mm, glandular or woolly, glandular-ciliate; corolla tubular-campanulate, yellow or orange to carmine, ca. 3.5 cm, glabrous; lobes 5, ovate, ca. 1.3 × 1.8 cm, emarginate; stamens 10, 2–2.7 cm, filaments pubescent at base; ovary with truncate apex, ca. 5.6 mm; woolly-tomentose and glandular-setose; style ca. 2.4 cm, glabrous; stigma capitate. Capsule 8–12 mm. Fl. Jun–Jul.
Alpine meadows, cliffs; 3600–5400 m. SE Xizang, NW Yunnan.
Two varieties occur in China; intermediate between them is subsp. rubens Cowan (Notes Roy. Bot. Gard. Edinburgh 20: 76. 1940; R. horaeum I. B. Balfour & Forrest var. rubens (Cowan) Davidian), described from Xizang. Rhododendron chaetomallum I. B. Balfour & Forrest var. xanthanthum Tagg & Forrest (Notes Roy. Bot. Gard. Edinburgh 15: 308. 1927; R. xanthanthum (Tagg & Forrest) D. F. Chamberlain), described from Xizang, is almost certainly a hybrid of R. citriniflorum.
