A small evergreen shrub 1 to 4 ft high; young shoots scaly. Leaves oblong-lanceolate to oblong-obovate, rounded or pointed at the mucronate apex, mostly tapered at the base, 11⁄4 to 5 in. long, 1⁄2 to 13⁄4 in. wide, sprinkled with tiny black glands above, glaucous and very scaly beneath; stalk 1⁄6 to 1⁄4 in. long. Flowers opening in April or May in a truss of three to nine; pedicels 3⁄8 to 11⁄8 in. long. Calyx deeply five-lobed, the lobes more or less scaly, membranous, 1⁄4 in. long, rounded. Corolla funnel-shaped, 1 to 15⁄8 in. long and wide, varying from pale pink to rosy crimson and crimson purple, sometimes almost white, five-lobed, the lobes roundish ovate. Stamens ten, slightly downy at the base. Ovary densely scaly, deeply grooved; style scaly towards the base, sometimes for more than half its length. Bot. Mag., t. 9343. (s. Boothii ss. Tephropeplum)
R. tephropeplum was discovered by Farrer in 1920, a few months before his death. He found it on the Chawchi and Maguchi passes, between the Nmai Hka and the Salween, ‘abundant on rocks and cliffs, forming wide and often procumbent masses’. The synonymous name R. spodopeplum is founded on a specimen he collected the same season on the crags of Shing Hong. It was introduced by Forrest in the following year from farther north on the same divide, where the Nmai Hka becomes known as the Taron or Kiu-chiang. Subsequently it was found to have a wide range to the westward, through upper Burma and the Mishmi Hills to the eastern end of the Himalaya.
R. tephropeplum is a very variable species. In habit it may be dwarf and compact, or laxly branched and up to 6 ft high. The flowers range in colour from almost white through clear pink to magenta pink, and there is also variation in size of leaf and in the number of flowers in each truss. The most noteworthy introductions are as follows:
Forrest 26431, from cliffs and rocky ledges on the Nmai Hka-Salween divide, at 11,000 ft. According to the field note, the plants had almost pure white flowers, which is true of some of the garden plants raised from this batch of seed.
Forrest 25572 and 25714, from screes and rocky slopes at 13,000 to 14,000 ft, on the Salween-Kiuchiang divide around 27° N. Plants 2 to 3 ft high, with rose-coloured flowers.
Kingdon Ward 8165. This is the type-collection of R. deleiense, now included in R. tephropeplum, but originally distinguished from it by the larger leaves and more numerously flowered inflorescence. It is a comparatively dwarf and compact form with flowers of a deep purplish rose, hardy, and usually not flowering until early May. It was found by Kingdon Ward in the Delei valley, Assam, in 1928, on rocky ridges and in thickets, at 8,000 to 9,000 ft.
KW 6794, from the Seinghku valley, north-west upper Burma, a compact form with flesh-pink to white flowers. KW 6834, a sparsely branched form with rose-purple flowers, is from the same valley.
KW 6303. This was found by Kingdon Ward in November 1924 in the Tsangpo gorge at the eastern end of the Himalaya, growing 6 to 8 ft high in Abies forest. A large-leaved form.
KW 20844, a dwarf form introduced by Kingdon Ward during his last expedition to Burma in 1953. It is in cultivation in the Savill Garden, Windsor Great Park.
Eight years after it was introduced, Lionel de Rothschild wrote of R. tephropeplum ‘There is something distinctive about this dwarf which is difficult to describe. The shape and habit and foliage is not particularly striking, but it is so friendly, so lavish in distributing its little clear coloured flower heads at every possible point at which they can be produced that you cannot help taking to it at first sight.’ Two years later he added: ‘My opinion of Rhododendron tephropeplum increases with each new variety of the species that I see in flower’ (New Flora and Sylva, Vol. 1, p. 163, and Vol. 4, p. 9). Although its flowers and expanding buds may be killed by frost it is winter hardy and needs only a sheltered position and shade from the hottest sun; in too much shade it becomes leggy and the flowers take on a bluish magenta tinge.
R. tephropeplum received an Award of Merit when shown from Bodnant on April 30, 1929, and again on April 30, 1935, as R. deleiense, shown by Lord Swaythling, Townhill Park, Hants.