An evergreen shrub 2 to 8 ft high in the wild, sometimes a small tree up to 15 ft high; young stems stout, glabrous or almost so. Leaves thick and leathery, elliptic, oblong-elliptic, oblong-lanceolate, or oblong-ovate, 2 to 41⁄2 in. long, 3⁄4 to 2 in. wide, acute or obtuse at the apex, base rounded, obtuse or slightly cordate, dark green and glabrous above, lower surface coated with a close, continuous, often rather spongy felt with a glossy skin, varying in colour from silvery white to fawn or pale yellow; petiole 3⁄8 to 3⁄4 in. long, glabrous. Flowers twelve to twenty in a fairly dense truss, opening in April; rachis up to 5⁄8 in. long; pedicels 3⁄8 to 11⁄2 in. long, glabrous or slightly floccose. Calyx very small. Corolla varying from white to rose, spotted with crimson, five-lobed, funnel-campanulate to cup-shaped, up to 2 in. across. Stamens ten, downy at the base. Ovary glabrous, conoid; style glabrous, with a discoid stigma. Bot. Mag., n.s., t. 147. (s. and ss. Taliense)
R. aganniphum has a wide distribution, from the Muli region of S.W. Szechwan through N.W. Yunnan to the Tibetan side of the Assam Himalaya; discovered by Kingdon Ward in 1913 on the Doker La (Mekong-Salween divide) and introduced by him in the same year. The type of R. vellereum, here included in R. aganniphum, was collected, also by Ward, in Tibet above the Tsangpo river, near Nang Dzong, in the transition zone where forest and alpine scrub gives way to xerophytic vegetation. The flower truss figured in the Botanical Magazine is from a plant raised from KW 5656, the original introduction, collected in the same area, where 40° F. of frost is not uncommon in winter. Seeds sent later by Ludlow and Sherriff are also from this part of Tibet. R. aganniphum is quite a pretty rhododendron but flowers too early for most gardens. In some forms the leaf-indumentum is remarkably thick and spongy.