A compact twiggy shrub with erect or interlacing stems, up to about 3 ft high, sometimes ground-hugging. Leaves less than 1⁄2 in. long, elliptic to roundish, obtuse or rounded at the apex, scaly on both sides, the scales beneath close or contiguous, brown, but intermixed with less numerous darker ones. Flowers solitary or in pairs. Calyx well developed, usually as long as the ovary, the lobes scaly on the back and at the margin. Corolla purple, lavender, or pink, about 3⁄4 in. wide. Stamens usually ten, occasionally fewer, downy in the lower part. Style glabrous, or sometimes downy at the base, usually longer than the stamens. (s. Lapponicum)
A native of the Himalaya at high altitudes from Nepal eastward and of the trans-Himalayan ranges of S.E. Tibet where it reaches farther into the dry zone than any other rhododendron; its southern limit is the Diphuk La, near the common border of Burma, Assam, and Tibet (KW 7058). It is in cultivation but uncommon.
subsp. boreale Philipson & Philipson R. nigropunctatum Franch.; R. ramosissimum Franch.; R. alpicola Rehd. & Wils.; R. violaceum Rehd. & Wils.; R. oresbium Balf. f. & Ward; R. stictophyllum Balf. f.; R. vicarium Balf. f.; R. batangense Balf. f.; R. oreinum Balf. f.; R. yaragongense Balf. f. – Calyx shortly lobed or reduced to a shallow cup. Style usually shorter than the stamens. Colouring of the scales on the underside of the leaf sometimes more uniform than in typical R. nivale.
This subspecies, with the synonyms listed above, was constituted by M. N. and W. R. Philipson in the revision of the Lapponicum group, published in 1975 (see p. 572). It occurs in W. Szechwan, bordering parts of Tibet and N.W. Yunnan. The first introduction appears to have been by Wilson from W. Szechwan when collecting for Messrs Veitch (seed-number 1543) and was grown as R. nigropunctatum (Bot. Mag., t. 8529). At the present time there are plants from Rock 24385 in the Edinburgh Botanic Garden, previously grown as R. stictophyllum, but the rhododendron in commerce under this name agrees none too well with R. nivale subsp. boreale and indeed bears some resemblance to R. lysolepis. It is, however, one of the prettiest of the Lapponicums.
The authors remark that the type of R. edgarianum Rehd. & Wils., collected by Wilson in W. Szechwan in 1908, appears to be a hybrid of R. nivale subsp. boreale with some undetermined species. He sent seeds, but the plants now grown as R. edgarianum, at least those seen, are from Forrest 16450, collected on the Beima-shan. The seed was distributed as R. oresbium, which is included in R. edgarianum in Species of Rhododendron, whence its present name. However, in the Philipsons' revision R. oresbium is included in R. nivale subsp. boreale, while Forrest's original specimen under 16450 is referred to R. tapetiforme (a species not treated here). The plants themselves do not agree either with R. nivale subsp. boreale nor with R. tapetiforme (nor with R. edgarianum). This “R. edgarianum” is a quite useful Lapponicum, of dwarf, erect habit, bearing light purple flowers at the end of May.