Rhododendron longipedicellatum Lei Cai & Y.P. Ma, sp. nov. (Figs. 1 & 2)

Diagnosis: —The new species most closely resembles Rhododendron rushforthii in its apiculate leaf blade apex, 3–8-flowered inflorescence, yellow flowers, undeveloped calyx with triangular lobes, campanulate corolla with pubescent mouth, orange anthers, and arched style. It differs from R. rushforthii in its whorled (versus scattered) leaves, obovate to oblong-obovate (versus elliptic) leaf blade, rounded, emarginate leaf apex (versus broadly acute, not emarginate), 3–4.2-cm-long pedicel (versus 1–2.2 cm), 0.8–2-mm-long ovate or triangular calyx lobes (versus 3–4 mm, triangular), and 1–1.8-cm-long stamens (versus 0.8–0.9 cm long).

Type: — CHINA. Yunnan: Malipo County, Babu Community, Nadeng village, Xiaonong, ca. 1197 m a.s.l., 104°56 ′ 50.73 ″ E, 28°23 ′ 02.60 ″ N, 13 December 2014 (fl.), Z. L. Dao. & Y. P. Ma DZL3637-1 (holotype KUN!, isotype KUN!).

Multi-branched shrubs 1–2.5 m tall; young shoots slender, long, glandular-scaly. Petiole 4–7 mm, deep red or occasionally green, sparsely scaly; leaves whorled, lamina leathery, obovate or oblong-obovate, 4–7.5 × 2–3.8 cm; base cuneate, narrowly decurrent, margin slightly revolute; apex rounded, emarginate, apiculate; abaxial surface pale green, scales scattered, brown; adaxial surface dark or fresh green, scaly or not, the lateral veins 4–8 pairs, midvein and lateral veins raised abaxially, concave adaxially. Inflorescence terminal, umbellate, 4–7-flowered. Pedicel 3–4.2 cm, sparsely glandular-scaly, white-pubescent; calyx lobes 5, 0.8–2 mm, ovate or triangular, scaly abaxially and on margin; corolla campanulate, pure yellow without blotch or spots, 1.5–2 cm, tube 0.7–1 cm, outer surface finely scaly, mouth pubescent; lobes broadly elliptic, ca. 1.2–1.5 × 0.6–0.9 cm; stamens 10, 1–1.8 cm, unequal, as long as or shorter than corolla; filaments densely white-pubescent in lower half but glabrous at base and apex; anthers orange, ca. 0.4 cm; ovary 5-locular, ca. 5 mm, densely white-pubescent; style arched, 0.7–1 cm. Capsule densely pubescent, ca. 1 cm, dehiscing from top; persistent style ca. 0.4 cm. Seeds unknown.

Distribution and ecology — Rhododendron longipedicellatum is known only from the type locality where it is represented by three populations in limestone areas at 1180–1250 m a.s.l. in Babu Community, Malipo County, SE Yunnan, China. The largest population in Nadeng village comprises about 350 mature plants, with the other two populations in Xiaonong each comprising ca. 80 individuals. Rhododendron longipedicellatum is found in habitats dominated by limestoneloving vegetation, dominated by Pistacia weinmanniifolia J. Poisson ex Franchet (Anacardiaceae) and Cyclobalanopsis glaucoides Schottky (Fagaceae), and occurs together with Paphiopedilum malipoense S.C. Chen & Z.H. Tsi (Orchidaceae), Paphiopedilum micranthum Tang & F.T. Wang (Orchidaceae), Tsuga sp. (Pinaceae), Taxus sp. (Taxaceae) and Mahonia sp. (Berberidaceae).

Phenology —Flowering from December to January, fruiting after February.

Etymology —The epithet “ longipedicellatum ” refers to the relatively long pedicels of the new species. This species has almost the longest pedicels in R. subsect. Pseudovireya (Clarke) Sleumer. The Chinese name in Pinyin is “chang geng du juan”.

Similar species — Rhododendron longipedicellatum is most similar to R. rushforthii, originally described from Sapa District, Lao Cai Province, N Vietnam and also distributed in S Yunnan. It can be distinguished from R. rushforthii by its arrangement of leaves, the shape and color of the lamina, the length of the petiole and the size of the calyx lobes (Table 1). Two other species, R. trancongii and R. datiandingense found in Hoa Binh Province, Vietnam and Guangdong Province, China are similar to R. longipedicellatum in their multi-flowered umbels but can be easily distinguished by the color and shape of the lamina, the leaf apex, lengths of the petiole, pedicel and stamens, and the indumentum of the ovary (Table 1).