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Erect free-growing shrub, to 2 m; young shoots covered with setae. Leaves (2.5-) 4-7.2 x 1-2 cm, elliptic to linear-obovate, apex acute or acuminate, margin fringed with long white hairs, upper surface with midrib impressed, lower surface with unequal scales their own diameter apart. Flowers 2-3, in a loose inflorescence, not scented; calyx disc-like, weakly ciliate; corolla white, sometimes flushed pink, often with a yellow blotch, openly-funnel-campanulate, 40-55 mm, outer surface pilose at base and variably scaly; stamens 10; ovary scaly, impressed below the style that is scaly below. Flowering April-May. Royal Horticultural Society (1997)
Distribution India NE
Habitat 1,450-2,300 m
RHS Hardiness Rating H3
Conservation status Critically endangered (CR)
An evergreen shrub of rather open thin habit, 8 or 10 ft high; young shoots, leaves, flower-stalks, calyx, and ovary scaly. Leaves oblanceolate to obovate, usually broadest above the middle, tapered at the base, pointed; 11⁄2 to 3 in. long, 1⁄2 to 11⁄2 in. wide; glossy green above, glaucous beneath; margins and leaf-stalks usually fringed with long hairs when young. Flowers sweetly scented, produced two to four together in May and June. Calyx very small; flower-stalks up to 1⁄2 in. long. Corolla funnel-shaped, 2 to 21⁄2 in. long; white tinged with pink, yellow in the throat, with the five lobes roundish ovate and about 1 in. long. Stamens ten, shorter than the corolla, densely clothed with hairs on the lower half. Ovary six-celled; style well protruded, scaly at the base. Bot. Mag., t. 4457. (s. Maddenii ss. Ciliicalyx)
Native of Assam in the Khasi, Jaintia, and Naga Hills, and of N.W. upper Burma; introduced about 1845 by Gibson (who collected plants for the then Duke of Devonshire) and named after him by Paxton. But it had been discovered in 1815 and previously named by Wallich in 1832. In the south and south-western counties it succeeds well out-of-doors, but in our average climate needs protection in winter. Being easily cultivated and bearing charmingly fragrant flowers, it has long been a favourite. Some beautiful hybrids have been raised from it crossed with R. edgeworthii, e.g., ‘Fragrantissimum’ and ‘Sesterianum’. Crossed with R. nuttallii it is a parent of ‘Tyermanii’.
A beautiful form of R. formosum, grown under glass at Edinburgh, received an Award of Merit in 1960. The flowers are flushed with pale orange in the throat and slightly tinged with pink on the outside. There is a similar plant in the Temperate House at Kew.
var. inaequale C.B.Cl. R. inaequale (C.B. Cl.) Hutch. – Mentioned on page 795 as a species, this has been restored to its original status as a variety of R. formosum. It was originally described by C.B. Clarke from a specimen collected by the younger Hooker in the Khasi hills.
R. iteophyllum, mentioned on page 664 as a species related to R. formosum, is included in it by Dr Cullen. Although it no longer matters, the spelling used is correct, not R. iteaphyllum (cf. Hutchinson in Bot. Mag., n.s., t. 563).
† R. coxianum Davidian – This was described in 1972 from a cultivated plant raised from seeds collected by Cox and Hutchison in 1965 in the Apa Tani valley of the Assam Himalaya (Arunachal Pradesh). See further in Peter Cox, The Larger Species of Rhododendron, p. 224 and plate 31. It is near to R. formosum.
R. formosum var. salicifolium C. B. Cl
R. iteaphyllum Hutch.
Leaves 10-16mm broad. Royal Horticultural Society (1997)
AM 1960 (Royal Botanic Garden, Edinburgh); flowers white, pale orange in throat internally, slightly pink-stained externally. AM 1979 (Mrs E. Mackenzie, Fressingfield, Norfolk) to a clone 'Lucy Elizabeth', as R. iteaphyllum. Flowers in trusses of 2-3; corolla white, flushed yellow, white in upper throat. AM 1988 (P.A. Cox, Glendoick) to a clone 'Khasia', from Cox and Hutchison 320; trusses 3-4-flowered, corolla white, with slight flush of greyed yellow in throat, strongly fragrant. AGM 199
Those forms with linear leaves have been referred to R. iteaphyllum. However, in the wild there is a complete gradation between these forms and those that match the type of R. formosum. Royal Horticultural Society (1997)
R. inaequale Hutch.
Leaves 15-21mm broad. Royal Horticultural Society (1997)
Meghalaya, Manipur, Arunachal Pradesh
AM 1947 (Lord Aberconway, Bodnant) as R. inaequale; flowers white, with a yellow band on posterior lobe, sweetly scented. FCC 1981 (Mrs E. Mackenzie, Fressingfield, Norfolk) as R. inaequale to a clone 'Elizabeth Bennet', from Cox & Hutchison 301; truss 3-5-flowered, corolla white with a blotch of yellow-green in the upper throat.
The broad-leaved var. inaequale is more widespread in the wild than var. formosum. Royal Horticultural Society (1997)