155. Rhododendron sargentianum Rehder & E. H. Wilson in Sargent, Pl. Wilson. 1: 504. 1913.
水仙杜鹃 shui xian du juan
Small shrubs, usually prostrate, 0.3–0.6 m tall; branchlets short, twiggy; young shoots densely scaly; bud scales persistent. Petiole 2–4 mm; leaf blade aromatic, elliptic, broadly elliptic, or ovate, 0.8–1.6(–2) × 0.3–0.8(–1.1) cm; base rounded or broadly cuneate; apex rounded, mucronate; abaxial surface pale brown, scales overlapping, long-stalked, lacerate, arranged in 2–3 tiers, those of lowermost tier golden, paler than the rest; adaxial surface dark green, shiny, scaly when young, glabrescent. Inflorescence 5–7(–12)-flowered. Pedicel 0.2–0.8 cm; calyx lobes (2–) 3–4(–6) mm, oblong to obovate, persisting to enclose mature capsule, scaly, margin strap-shaped-ciliate; corolla narrowly tubular, whitish yellow, 1–1.6 cm, tube 6–9 mm; outer surface scaly on tube and at bases of lobes, inner surface densely pilose; stamens 5, included in corolla tube, filaments glabrous; ovary 1–1.5 mm, scaly; style thick, straight, nearly as long as ovary, glabrous. Capsule ovoid, ca. 4 mm, scaly. Fl. May–Jul, fr. Oct.
Cliffs, exposed rocks; 3000–4300 m. C and W Sichuan.
Rhododendron praeclarum I. B. Balfour & Farrer (Notes Roy. Bot. Gard. Edinburgh 9: 261. 1916), from Gansu (Min Shan), is described as having bright yellow (“flava”) flowers. It differs from R. sargentianum, the yellow-flowered species to which it is most closely allied, as the calyx lobes are fringed with scales, not loriform ciliae. Cullen (Notes Roy. Bot. Gard. Edinburgh 38: 167. 1980) considered that R. praeclarum was almost indistinguishable from R. primuliflorum, but noted that the type locality is disjunct. If the flower color is correct then this affinity seems unlikely.