An evergreen shrub of rather diffuse habit, 8 to 10 ft high; young shoots bristly and slightly scaly. Leaves narrowly oval, or oblanceolate, tapered at both ends, pointed, 21⁄2 to 41⁄2 in. long, 1 to 2 in. wide, dark glossy green above, glaucous-green beneath and thickly sprinkled with golden-brown scales; stalk 1⁄3 to 1⁄2 in. long, bristly and slightly scaly. Flowers produced in March and April in a terminal truss of usually three blossoms. Flower-stalks 1⁄2 in. long, stout, scaly. Calyx five-lobed, the lobes 1⁄8 in. long, conspicuously fringed with white bristles 1⁄8 in. long. Corolla pure white except for a yellow stain on the upper side of the tube; the base is funnel-shaped, the five rounded wavy lobes spreading and giving the flower a diameter of 4 in. Stamens ten, about 2 in. long, white, very hairy at the base. Ovary scaly; style 21⁄2 in. long, scaly at the base. Bot. Mag., t. 7782. (s. Maddenii ss. Ciliicalyx)
R. ciliicalyx was discovered by the Abbé Delavay in 1884 in W. Yunnan, in the mountains east of Lankiung (north of Lake Tali), and was introduced from Paris to Kew in 1892, first flowering there in 1900. It was later reintroduced by Forrest from the borders between Yunnan and Burma and more recently by Kingdon Ward from the Triangle, during his last expedition to Burma (1953). According to him R. ciliicalyx is not usually an epiphyte. ‘On the contrary, it is more often a slim shrub ten to twelve feet high … though it needs strong support from the surrounding thicket to keep it upright. Out of bloom, its shining plum-purple bark betrays it… . Very occasionally it is an epiphytic shrub, appearing as a pale summer cloud in a big tree’ (Return to the Irrawaddy, p. 161).
This beautiful species, one of the very finest of white rhododendrons, grows well in the Temperate House at Kew, where it has protection from more than one or two degrees of frost. Here it is covered with blossom every spring. It is only likely to succeed out-of-doors in the milder parts of Cornwall and similar places. The flowers are sometimes pink and they have a faint sweet fragrance. It is closely related to the much hardier Himalayan R. ciliatum, whose style has no scales and whose habit is dwarfer, more spreading and bushy. The bristly calyx is distinctive.
Although not the oldest species in its group, R. ciliicalyx has been taken as the ‘type’ of a large and taxonomically difficult subseries of the Maddenii series. In this some thirty-five species have been placed, many of them distinguished by unreliable characters. In a cursory study of the subseries, Dr Sleumer has reduced the number to twenty and remarks that still more drastic reduction may be necessary (‘The Genus Rhododendron in Indochina and Siam’, Blumea, Suppl. IV (1958), pp. 40-7). There can be no doubt that most of his judgements will be upheld when the group is subjected to a detailed revision, but in the meantime it seems best to maintain those of the reduced species which are familiar in cultivation. See also R. johnstoneanum and R. veitchianum.
R. carneum Hutch. – In describing this species (Bot. Mag., t. 8634) Dr Hutchinson remarked that it is very near to R. veitchianum (q.v.), differing in its smaller, flesh-pink, unblotched flowers, and smaller, more ciliate calyx lobes. However, Dr Sleumer places it under R. ciliicalyx in synonymy, and certainly it strongly resembles that species also. It was described from a cultivated plant raised from seeds collected in the Northern Shan States, Burma, in 1912 and is therefore intermediate geographically between the two species. It is tender. Award of Merit April 5, 1925, when shown by Lionel de Rothschild from Exbury.
R. dendricola Hutch. – A very tender species from upper Burma at low elevations, discovered by Kingdon Ward in the valley of the Nmai Hka (upper Irrawaddy) in 1914, growing as an epiphyte on tall trees, and was later found by him as far west as the Mishmi Hills, Assam. The truss figured in Bot. Mag., t. 9682, was from a plant raised from Forrest 26459, collected on the Nmai Hka-Salween divide at 9,000 ft. R. dendricola resembles R. ciliicalyx in general aspect, and is included in it by Sleumer, but it differs in the very small rim-like calyx and in having the corolla scaly outside. The flowers are white or white tinged with pink, sometimes barred with pink on the outside, with a yellow flare in the throat, fragrant, up to 4 in. long, in trusses of three or four.
R. scottianum Hutch. – In Bot. Mag., t. 9238, where this species is figured, Dr Hutchinson remarks that it is really very near to R. ciliicalyx, but the bristlelike ciliations on the calyx are fewer or wanting, the scales on the undersurfaces of the leaf are denser, the corolla is scaly outside, and the style is scaly up to the mid-point or beyond. It was discovered by Forrest near Tengyueh in Yunnan, near the frontier with Burma, and introduced by him. It is a very tender but beautiful species, with fragrant white or rose-flushed flowers up to 4 in. long. It is difficult to agree with Dr Sleumer that this species is the same as R. lyi (q.v. under R. johnstoneanum), from which it differs in having branchlets without bristles, leaves generally broader, with the scales beneath much closer, and larger flowers.
R. supranubium Hutch. – A close ally of R. ciliicalyx and included in it by Sleumer, but perhaps distinct enough to rank as a separate species. The leaves are thinner and smaller, elliptic to oblanceolate-elliptic, 11⁄2 to 25⁄8 in. long, 1⁄2 to just over 1 in. wide. The corolla is smaller, and though the young shoots, petioles, base of leaf-blades, and calyx-lobes may have a few weak hairs at first, these seem to be soon lost. It was described from specimens collected by Forrest on the eastern flank of the Tali range, W. Yunnan, in rocky situations at 11,000 to 12,000 ft, and was introduced by him in 1910. Farrer and Cox reintroduced it in 1919 from near Hpimaw on the Nmai Hka-Salween divide, upper Burma, growing as an epiphyte at 8,000 ft, ‘with very large and lovely flowers, intensely fragrant, of pure rose-flushed white with a yellow base… . A most exquisite beauty’ (Farrer 848). R. supranubium seems to be uncommon in cultivation and has never received an award.