A usually dwarf, evergreen shrub of densely branched, close growth; young shoots thinly scaly. Leaves obovate, tapered at the base, rounded but with a short mucro at the apex; margins recurved and crinkled, 1⁄3 to 1 in. long, 1⁄8 to 1⁄2 in. wide, dark bright green and glabrous above, pale green or slightly glaucous beneath and slightly scaly at first; stalk 1⁄10 in. long. Flowers solitary or in twos or threes at the end of the shoot, nodding, each produced on a slender, slightly scaly stalk 1 to 11⁄2 in. long. Calyx five-lobed; the lobes 1⁄5 in. long, glabrous. Corolla of various shades of purple from rosy to plum-coloured or almost black purple, widely bell-shaped, 5⁄8 in. long, five-lobed, the lobes rounded and scarcely recurved. Stamens ten (sometimes eight or twelve), downy and widened towards the base; anthers yellowish brown. Ovary glandular-scaly; style glabrous, purple, decurved so as to protrude between the lower lobes of the corolla. Bot. Mag., t. 9407A. (s. Campylogynum)
R. campylogynum ranges throughout the rainiest part of the Sino-Himalayan region, from the Tali range and the Mekong-Salween divide in the east through upper Burma to the eastern Himalaya, at altitudes of 11,000 to 15,000 ft (rarely lower). It is therefore one of the most alpine of rhododendrons. It was discovered by the Abbé Delavay in 1884 in the Tali range, whence it was introduced by Forrest in 1912. In the following year Kingdon Ward collected seeds near one of the glaciers of the Ka-kar-po group, on the borders between Yunnan and Tibet. The plants there 'appeared to have black or deep plum-coloured flowers. When, however, the sun shone through them, the flowers were seen to be blood-red, which is how they would appear to their bee-visitors, since the flowers stand horizontally' (Mystery Rivers of Tibet, p. 75).
This pleasing species flowers in May and is admirable for the rock garden by reason of its neat habit and rich purple flowers. In some forms, however, the flowers are purplish pink or flesh-pink. In the clone named 'Thimble', they are salmon-pink (Award of Merit, May 23, 1966, when shown by Capt. Collingwood Ingram, The Grange, Benenden, Kent).
A white-flowered form of R. campylogynum, grown by Capt. Collingwood Ingram at Benenden, Kent, received an Award of Merit when he exhibited it on June 12, 1973. He has given it botanical status as var. leucanthum (R.C.Y.B. 1969, p. 49) and it received the award under that name.
var. myrtilloides (Balf. f. & Ward) Davidian R. myrtilloides Balf. f. & Ward – Of dwarfer habit, with smaller flowers up to 1⁄2 in. or so long. This variety was discovered by Kingdon Ward in 1914 in upper Burma, on a spur of Imaw Bum at about 13,000 ft (not 15,000 ft as is sometimes stated). Most of the plants originally grown as R. myrtilloides were raised from three batches of seed collected in the same area in 1919. KW 3172 was from plants growing in a riverbed under Imaw Bum at 8,000 ft, growing in 'heath-like masses on slaty rocks' and with plum-coloured flowers. Apparently all the seed came from one plant; twenty years later he found it again during the Vernay-Cutting expedition and again took seed from it. He also collected seed on Imaw Bum itself at 12,000-13,000 ft, from plants with port-wine-coloured or flesh-pink flowers (KW 3303). The third collection was by Farrer and Cox from the Hpimaw ridge a short way south of Kingdon Ward's hunting-ground, at around 12,000 ft (Farrer 1046). 'Imagine yard upon yard of turf cushioned with masses of small, shining, dark-green leaves, out of which rise delicate glandular flower-stalks. From each hangs a single little bell-shaped trumpet of sculptured wax, a deep mahogany inside and a claret exterior that is covered with the bloom of a purple plum. There is another form, a uniform claret-mahogany inside and out' (Cox, Farrer's Last Journey, p. 98). Kingdon Ward later collected seed at the eastern end of the Himalaya (KW 5842, nicknamed by him “Plum Warner”), but the plants under this number were originally grown as typical R. campylogynum.
As a rock-garden plant the var. myrtilloides has all the virtues of the type, except that it has the reputation of being rather more difficult to cultivate well, at least in the Burmese forms originally introduced. It received an Award of Merit on June 6, 1925 (a pink-flowered form raised at Exbury from KW 3172) and a First Class Certificate on June 8, 1945 (a form with rose-magenta flowers, also from Exbury).
Other varieties recognised by Davidian are:
var. celsum Davidian – Of erect habit. Found by Forrest in the Tali range, Yunnan, growing 4 to 6 ft high.
var. charopoeum (Balf. f. & Farrer) Davidian R. charopoeum Balf. f. & Farrer; R. caeruleo-glaucum Balf. f. & Forr. – Flowers larger, up to 1 in. long. Introduced by Forrest.
var. cremastum (Balf. f. & Forr.) Davidian R. cremastum Balf. f. & Forr. – Of erect habit, up to 4 ft high in the wild, with larger leaves up to 11⁄2 in. long, pale green on both surfaces. Discovered and introduced by Forrest. Award of Merit May 24 1971, to clone 'Bodnant Red'.
From the Supplement (Vol. V)
Dr Cullen recognises no subspecies or varieties in this species, on the grounds that the variations it shows are not correlated nor 'geographically significant' (Rev. 1, pp. 145-6). The varieties previously recognised could, however, be maintained as horticultural groups (see Peter Cox, op. cit., p. 88).