太白杜鹃 tai bai du juan

Shrubs or small trees, 2–6 m tall; young shoots puberulent; bud scales ± persistent. Petiole 10–15 mm, puberulent, glabrescent; leaf blade leathery, oblong-lanceolate to oblong-elliptic, 6–9 × 2.5–3.5 cm; base cuneate; margin revolute; apex obtuse, mucronate; both surfaces glabrous; abaxial surface pale green; reticulate veins distinct. Inflorescence racemose-umbellate, 10–15-flowered; rachis ca. 10 mm, pale brown-tomentose. Pedicel 1–1.5 cm, densely whitish gray-pubescent; calyx lobes 5, 1–1.5 mm, broadly triangular, sparsely pubescent; corolla campanulate, pale pink or whitish, with purple spots on corolla tube on upper lobes, 2.5–3 cm, lobes 5; stamens 10, unequal, filaments densely puberulent in lower half; ovary conical, 4–5 mm, sparsely white-pubescent; style ca. 2.2 cm, glabrous, stigma capitate. Capsule cylindric, slightly curved, 10–30 × 4–8 mm. Fl. May–Jun, fr. Jul–Sep.

Forests, mountain slopes; 1800–3500 m. S Gansu, W Henan, S Shaanxi.

This species almost certainly does not belong in Rhododendron subsect. Taliensia; it probably has closer affinities with species in R. subsect. Selensia. In addition, R. purdomii var. villosum L. H. Wu (J. Wuhan Bot. Res. 17(1): 21. 1999), described from W Henan (Songxian), needs to be considered. It was described as differing from var. purdomii in having the leaf blade larger, 4–11 × 2–5.5 cm, adaxially sparsely yellowish villous, the margin densely ciliate, with both villi and ciliae readily deciduous; the petiole longer, to 3 cm; and the inflorescence rachis longer, to 1.8 cm.