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Shrub or small tree, 1-14 m. Leaves 5.5-19(-30) x 2.2-11 cm, elliptic to ovate, base rounded, glabrous. Flowers 5-10, in a lax truss, 6-8-lobed, scented, white, sometimes flushed rose, sometimes also with purple flecks, open- to funnel-campanulate, nectar pouches lacking, 45-100 mm; stamens 14-20, hairy below; ovary and style covered with stalked glands that are usually white. Flowering May-June. Royal Horticultural Society (1997)
RHS Hardiness Rating H6
Conservation status Least concern (LC)
An evergreen shrub variable in habit, some forms being dense and bushy, others erect and attaining a height of 25 ft in cultivation; young stems glabrous. Leaves leathery, oblong to oblong-elliptic or broadest slightly above or below the middle, 2 to 6 in. long, 11⁄8 to 27⁄8 in. wide, obtuse to rounded at the apex, cuneate-rounded at the base, medium green and glabrous above, glaucous green beneath and glabrous there except for minute down not visible to the naked eye; petiole 3⁄4 to 11⁄8 in. long, glabrous. Flowers fragrant, usually eight to ten in a terminal cluster on a more or less glandular rachis 1 in. or slightly more long; pedicels glandular, up to 15⁄8 in.long. Calyx very small, six- or seven-lobed, glandular. Corolla widely funnel-campanulate, 2 to 3 in. across at the mouth, white or rose-coloured, hairy inside at the base, six- to eight-lobed, the lobes rounded. Stamens twelve to eighteen, the filaments downy at the base. Ovary densely glandular; style covered throughout with white or yellowish glands. Bot. Mag., t. 8659. (s. and ss. Fortunei)
R. decorum is one of the most widely spread of Chinese rhododendrons. It was introduced by Wilson in 1901 from near Kangting (Tatsien-lu) in W. Szechwan; he later sent seeds from Mupin in the same province, where the Abbé David discovered the species in 1869. Later sendings by Forrest, Kingdon Ward, and Rock, are from various parts of Yunnan, where R. decorum seems to be very common in the less rainy parts, often growing on sunny, brackeny slopes or in open woodland of Pinut armandii. In Burma it seems to be uncommon, though Farrer and Cox sent seeds of a large-leaved tender form from the borders between it and Yunnan. According to Kingdon Ward, the flowers of R. decorum were eaten in Tali, and called the ‘white-flowered vegetable’.
R. decorum varies in hardiness, as might be expected from its wide range. The largest-flowered forms are tender, while some of the hardier forms are worthless, with papery, crumpled flowers. It also varies in habit, flowering-time, and the colour of the flowers.
Flowers 45-60mm; leaves 5.5-15cm.
Distribution NE Burma, SW China (Yunnan, Sichuan, Guizhou).
Awards AM 1923 (Lt Col L.C.R. Messel, Nymans, Sussex) to a clone ‘Mrs. Messel’; flowers pure white, broad and open, in a truss of c.12.
R. diaprepes Balf.f & W.W.Sm.
Flowers 65-100mm; leaves 12-19(-30)cm long.
Distribution NE Burma, China (S Yunnan), Laos.
Awards AM 1926 (L. de Rothschild, Exbury) to subsp. diaprepes; flowers white, tinged pink externally. AM 1953 (Mrs R.M. Stevenson, Tower Court, Ascot) and FCC 1974 (Crown Estate Commissioners, Windsor) to a clone ‘Gargantua’, as R. diaprepes, from Forrest 11958; flowers very large, white, with a green basal flush.
Subsp. diaprepes is larger in all its parts than is subsp. decorum but otherwise the two are very similar. It comes from the humid part of the range of the species and generally occurs at relatively modest altitudes.