An evergreen shrub rarely more than 6 or 7 ft high in cultivation, but said to be sometimes a small tree in the wild; young shoots, undersurface of leaves, and flower-stalks thickly covered with a pale brown felt. Leaves obovate to narrowly oval, rounded at the end, 21⁄2 to 5 in. long, 1 to 21⁄4 in. wide, upper surface at first covered with whitish wool which ultimately falls away except at the base of the midrib, leaving it dark green; stalk 1⁄4 to 1⁄2 in. long. Flowers in a terminal cluster of usually six or seven but sometimes ten, opening in April, on stalks 1⁄2 to 3⁄4 in. long. Calyx very small. Corolla 2 to 21⁄2 in. wide, bell-shaped, five-lobed, pale yellow dotted with red, the lobes rounded, 3⁄4 in. wide. Stamens ten, downy at the base; anthers dark brown. Ovary woolly; style glabrous. (s. Campanulatum)
Native of the Himalaya from E. Nepal eastward; discovered by J. D. Hooker late in 1848 in E. Nepal, at 10,000 to 12,000 ft, and introduced by him. Lionel de Rothschild wrote of this species: 'R. lanatum ... is the most difficult member of this series to cultivate in our climate. It has pretty yellow flowers, while its leaves have an attractive tawny, woolly tomentum underneath. It is hardy in most gardens, but cannot stand drought and, above all, requires more leaf soil than most rhododendrons, and unless it is given plenty of suitable woodland soil round the roots and beech haulm and oak leaves dug in and a good mulching of bracken or leaf soil on the top, is very ill-tempered and often looks a stubborn and seedy plant' (Year Book Rhod. Ass. 1934, p. 109).
var. luciferum Cowan – Leaves narrower, oblong, pointed at the apex. Described from specimens collected by Ludlow and Sherriff in S.E. Tibet in 1936, and introduced by them. The type is from the Bimbi La, in Tsari. In the field note they remark: 'Indumentum of dried leaf is skinned off and rolled up and sold as wicks for butter lamps' – whence the epithet luciferum.
R. tsariense Cowan – Leaves smaller than in R. lanatum, 1 to 21⁄2 in. long, 3⁄8 to 11⁄4 in. wide, rounded or slightly cordate at the base, very shordy stalked. Flowers pink, cream-coloured, or white, often spotted with pink. Discovered by Ludlow and Sherriff in the Tsari region of the Tibetan Himalaya in 1936 and introduced by them. According to the collectors' field notes the species varies in habit and may grow 12 ft high. Their seed-number 2766 was from plants 2 to 5 ft high, and an example at Edinburgh from this sending was only 2 ft high in 1960, when almost a quarter-century old. In 1964 an Award of Merit was given to clone 'Yum-Yum' with white flowers flushed with pink, exhibited by Maj. Gen. and Mrs Harrison, Tremeer, Cornwall, on April 7. The original plant, then about 4 ft high and as much across, was raised from Ludlow and Sherriff 2858, collected 1936; according to the field note, the parent plants were 8 to 10 ft high.
R. tsariense, in its dwarf forms, would be worth planting even if it never flowered. It makes a rugged, compact specimen, and the leaves, powdered with brown above all through the summer, become glabrous and rich olive-green in winter.
From the Supplement (Vol. V)
† R. lanatoides Chamberlain – A new species, described in 1982, the type of which is Ludlow, Sherriff and Elliot 13746, collected in south-east Tibet, but introduced earlier by Kingdon Ward (KW 5871) and perhaps in cultivation as R. roxieanum aff.