An evergreen shrub or small tree from 12 to 30 ft high, of straggling, thinly branched habit, often growing in nature as an epiphyte on the branches and forks of large trees; young shoots very stout, scaly. Leaves stout and leathery, oval, tapered at both ends, shortly pointed, 5 to 12 in. long, 21⁄2 to 41⁄2 in. wide, greyish, strongly reddish veined and thickly sprinkled with scales beneath, at first reddish above, ultimately pale green, much puckered and wrinkled. Flowers fragrant, usually three to six in a terminal truss (as many as eleven have been known), opening in May horizontally or rather nodding. Calyx deeply five-lobed, the lobes oblong, rounded at the end, 1 in. long, 1⁄2 in. wide. Corolla funnel-shaped at the base, of wax-like texture, ivory-white suffused with yellow in the throat, 4 to 5 in. long and measuring about the same across the five spreading, rounded lobes. Stamens normally ten, 21⁄2 in. long, downy towards the base; anthers 1⁄3 in. long, reddish brown. Ovary and base only of style scaly, the latter up to 3 in. long. Bot. Mag., t. 5146. (s. Maddenii ss. Megacalyx)
Native of the eastern Himalaya, S.E. Tibet, and upper Burma. It was discovered by Thomas Booth in 1849-50 in the Dafla Hills, Assam Himalaya, growing 'on the banks of the Papoo, swampy ground amongst Yews and Oaks at 4000-5000 ft'. It was introduced by him, and first flowered in 1858 with Otto Forster of Augsburg, who had bought a grafted plant from Standish and Noble three years previously. At Kew it flowered in the following year in the Rhododendron House, when 9 ft high.
In regard to the individual flower, which suggests a lily in size and texture, this is the most magnificent of rhododendrons. Flowers are frequently 6 in. wide. Unfortunately it is too tender to be grown in the open air even in Cornwall. It is not a strong-rooting shrub and likes a sandy, peaty, well-drained soil. Healthy plants make shoots one foot or more long in a season.
R. nuttallii received a First Class Certificate more than a century ago. The Award of Merit was given in 1955 to a form raised from Ludlow and Sherriff seeds, shown by the Sunningdale Nurseries.
The name var. stellatum was given by Hutchinson to a form with rather smaller flowers than normal and a spreading calyx, raised from seeds collected by Kingdon Ward in the Tsangpo gorge, S.E. Tibet, in 1924. Plants from these seeds (KW 6333) are said to be somewhat hardier than the common form. Award of Merit 1936.