5. Rhododendron megacalyx I. B. Balfour & Kingdon Ward, Notes Roy. Bot. Gard. Edinburgh. 9: 246. 1916.
大萼杜鹃 da e du juan
Shrubs or small trees, 1.5–3 m tall; old branches glabrous; young shoots stout, brownish purple, cylindric, densely scaly. Petiole shallowly grooved, 10–30 mm; leaf blade leathery, obovate-elliptic or elliptic, 10–17 × 2.5–7 cm; base narrowed; apex rounded, apiculate, sometimes slightly concave; abaxial surface pale white, scales dense, reddish brown, appressed; adaxial surface dark green, scales dense on young leaves, glabrescent. Inflorescence terminal, shortly racemose, 3–5-flowered. Flowers fragrant. Pedicel stout, 2.5–3 cm, glabrous; calyx campanulate, 5-lobed to middle, 20–30 mm, enlarging and persisting to enclose mature capsule, scales absent; corolla broadly funnelform, white, 6.5–9.5 cm; tube 50–60 mm; outer surface scaly on lobes, lobes suborbicular, ca. 3 cm wide; stamens 10, unequal, slightly shorter than corolla tube; filaments slender, lower part pubescent; ovary 5-locular, densely scaly; style slightly exserted; base sparsely scaly; stigma large, discoid. Capsule cylindric, ca. 20 mm. Fl. Apr–Jun.
Evergreen broad-leaved forests, Tsuga forests; 2200–3000 m. SE Xizang, NW Yunnan [NE India, NE Myanmar].