优秀杜鹃 you xiu du juan

Rhododendron coryphaeum I. B. Balfour & Forrest; R. semnum I. B. Balfour & Forrest.

Shrubs or trees, 3–7 m tall; young shoots 8–10 mm in diam., densely gray floccose-tomentose. Petiole stout, flattened and broadly winged, 1.5–2.5 cm, sparsely gray tomentose or glabrescent; leaf blade leathery, oblong-lanceolate to oblong-ovate, broadest near apex of blade, 15–38 × 6–14 cm; base cuneate with broad wings decurrent down petiole; apex rounded, sometimes emarginate; abaxial surface silvery-gray to buff, indumentum thin, compacted and agglutinated; adaxial surface glabrous; midrib and veins prominent abaxially. Inflorescence racemose-umbellate, 12–20-flowered; rachis 25–35 mm. Pedicel ca. 3.5 cm, floccose-tomentose; calyx lobes 7(or 8), 1.5–2.5 mm, tomentose; corolla obliquely campanulate, pale yellow, white flushed pink or pink, with crimson spots and basal blotch inside, 3.5–4.5 × ca. 5 cm wide, lobes 7(–8); stamens 14–16, unequal, filaments glabrous; ovary 8–10 mm, densely buff-tomentose; style ca. 2.6 cm, glabrous, stigma discoid. Peduncle 4.5–5 cm. Capsule oblong-cylindric, base strongly oblique, 30–40 × 6–10 mm, rusty-tomentose. Fl. May–Jun, fr. Aug–Oct.

Mixed forests, coniferous forests in alpine regions; 3100–4200 m. SE Xizang, NW Yunnan.