Creeping shrub, to 0.1 m; young shoots scaly and puberulent. Leaves 0.9-1.9 x 0.5-1.2 cm, elliptic to broadly elliptic, apex acute to rounded, margin entire, lower surface with distant small equal golden scales. Flowers 1-3, in a loose terminal inflorescence; calyx lobes oblong, 2-4 mm, not ciliate; corolla pink or purple, campanulate, slightly oblique, 11-21 mm, tube 7-14 mm, outer surface densely pilose, scales few, mostly on lobes; stamens 10; ovary scaly, impressed below the straight, glabrous style that is shorter than the stamens. Flowering April-June. Royal Horticultural Society (1997)
Distribution Bhutan Myanmar N China S Tibet India Sikkim, Arunachal Pradesh Nepal
Habitat 3,500-4,250 m
RHS Hardiness Rating H5
Awards AM 1935 (Lord Swaythling, Townhill Park, Southampton) from Kingdon-Ward 6961; flowers pinkish mauve.
Conservation status Least concern (LC)
Taxonomic note This species differs from the remaining species in the subsection in its small campanulate corolla and short style. Royal Horticultural Society (1997)
An evergreen dwarf shrub with scaly minutely downy branchlets. Leaves elliptic to obovate-elliptic, rounded to obtuse at the apex, 1⁄2 to 3⁄4 in. long, about half as wide, bright green or bluish green above, glaucous and scaly beneath (sometimes with a few scales on the upper surface also); leaf-stalks very short, scaly. Flowers solitary, in twos or threes, from terminal buds; pedicels up to 1 in. long, elongating in fruit. Calyx five-lobed, scaly, up to 1⁄8 in. long. Corolla campanulate, five-lobed, 1⁄2 to 3⁄4 in. long, pink or rose-coloured, downy and slightly scaly outside. Stamens ten, included. Ovary densely scaly; style straight, included in the corolla, glabrous. (s. Uniflorum)
R. pumilum was discovered by J. D. Hooker in 1849 in the Sikkim Himalaya. It was, he wrote, the smallest of all the rhododendrons he saw. ‘Its slender woody stem roots among moss, Andromeda fastigiata, &c., ascends obliquely, and bears a few spreading branches, 3 to 4 inches in length… . An extremely elegant species, and apparently very rare; for I have only gathered it twice, and each time in the wildest district of Sikkim, where its elegant flowers appear soon after the snow has melted, when its pretty pink bells are seen peeping above the surrounding short heath-like vegetation, reminding the botanist of those of Linnaea borealis.’
R. pumilum also occurs in E. Nepal, and to the east of Sikkim ranges as far as N.W. upper Burma. It was apparently not introduced, or at least not successfully, until Kingdon Ward found it on the Dohong La at the eastern end of the Himalaya in 1924, forming hassocks and mats on steep alpine turf. In 1926 he collected seeds from the Seinghku valley in Burma (KW 6961). This form, which he nicknamed “Pink Baby”, carried ‘solitary or paired flowers of a delicate shell-pink, hoisted above the crowded leaves on long crimson stalks …’. More recently seeds have been sent by Ludlow and Sherriff and also by Stainton (from E. Nepal).
R. pumilum is very distinct from R. uniflorum and its immediate allies in its campanulate flowers and elliptic leaves. Indeed, it bears a certain resemblance to R. campylogynum. It is quite hardy and suitable for the rock garden. The Award of Merit was given on April 30, 1935, to a form raised from KW 6961, exhibited by Lord Swaythling, Townhill Park, Hants.