泸水杜鹃 lu shui du juan

Small trees, ca. 3 m tall; older branchlets glabrous; branchlets stout; young shoots stellate-tomentose. Petiole cylindric, slightly grooved adaxially, 10–15 mm; leaf blade leathery, obovate-elliptic to elliptic, broadest above middle of blade, 9.5–12 × 3–4 cm; base cuneate; margin recurved; apex obtuse or cuspidate; both surfaces glabrous; abaxial surface pale tawny; adaxial surface green; midrib conspicuously raised abaxially, flat adaxially; lateral veins 16–19-paired, obscure on both surfaces. Inflorescence racemose-umbellate, 10–12-flowered; rachis ca. 15 mm, pubescent. Pedicel stout, 10–12 cm, yellowish stellate-tomentose; calyx cupular; lobes 5, 2–3 cm, stellate-tomentose, glabrous inside, margin ciliate; corolla tubular-campanulate, yellow, without flecks, 3.5–4 cm, lobes 5, suborbicular, ca. 1 × 1.5 cm, emarginate; stamens 10, 2–3 cm, filaments pubescent at base; ovary ovoid, ca. 7 mm, yellowish tomentose; style 3–3.5 cm, stellate-tomentose to tip, stigma small. Capsule not known. Fl. Jul.

Mixed forests; ca. 2700 m. W Yunnan.

This very rare species has a close affinity with Rhododendron facetum, but differs in the yellowish corolla. The apparent earlier homonym “Rhododendron flaviflorum Elmer” (Merrill, Enum. Philipp. Fl. Pl. 3: 244. 1923) was cited as a synonym of R. leytense Merrill and was therefore not validly published under Art. 34.1(c) of the Saint Louis Code.