473. Rhododendron moulmainense J. D. Hooker, Bot. Mag. 82: t. 4904. 1856.
毛棉杜鹃 mao mian du juan
Rhododendron klossii Ridley; R. leucobotrys Ridley; ?R. nematocalyx I. B. Balfour & W. W. Smith; R. oxyphyllum Franchet; R. pectinatum Hutchinson; R. siamense Diels; R. stenaulum I. B. Balfour & W. W. Smith.
Shrubs or small trees, 3–15 m tall; bark gray-brown, not peeling. Petioles stout, 10–15 mm, glabrous; leaf blade leathery, oblong-lanceolate or elliptic-lanceolate, 5–12 × 2.5–5 cm; base cuneate or broadly cuneate; margin revolute; apex acuminate to acute; both surfaces glabrous; lateral veins not reaching margin. Inflorescence subapical, 2- or 3-flowered. Pedicel 1–2 cm, glabrous; calyx lobes 5, shallowly undulate, small, glabrous; corolla narrowly funnelform, white, with a yellow blotch within, 4.3–5.5 cm, tube 15–20 × 3–4 mm in diam., lobes deeply divided, spreading, oblong-obovate, apex entire and rounded; stamens 10, unequal, 3.5–4 cm, slightly shorter than corolla, filaments flat, with silvery-white scurfy pubescence below middle; ovary long-cylindric, tapering into style, 5–10 mm, dark brown, glabrous; style ca. 5 cm, often shorter than corolla, slightly longer than stamens, glabrous. Capsule cylindric, apex acuminate, 35–60 × 4–6 mm; style persistent. Fl. Mar–Apr, fr. Jul–Dec.
Open forests, thickets; 700–1500 m. S Yunnan [NE India, Indonesia, Malaysia, Myanmar, Thailand].
Rhododendron nematocalyx is said to differ in its larger calyx. However, calyx size is in general extremely variable in this section; it is therefore uncertain whether this entity should be treated as a straight synonym of R. moulmainense or maintained as a variety of it.