Kindly sponsored by
Peter Norris, enabling the use of The Rhododendron Handbook 1998
Article from Bean's Trees and Shrubs Hardy in the British Isles
'Rhododendron oreotrephes' from the website Trees and Shrubs Online (treesandshrubsonline.
Shrub or small tree, 1–8 m; young shoots scaly. Leaves evergreen or semi-deciduous, often bluish, 2.1–6.3(–8.7) × 1.8–3.1(–4) cm, orbicular to oblong or obovate, apex rounded to acute, upper surface often slightly hairy along midrib, lower surface with dense (but not touching) reddish brown to grey, opaque narrow-rimmed scales, often puberulent below. Flowers 1–3(–4), in a loose terminal inflorescence; calyx minute, sometimes ciliate; corolla rose-pink to rose-lavender, with darker spots, rarely white, funnel-shaped to funnel-campanulate, 21–34 mm, outer surface lacking scales, glabrous; stamens 10; ovary scaly, impressed below the declinate, glabrous style. Flowering April-May. Royal Horticultural Society (1997)
Distribution China S Tibet, N Yunnan, SW Sichuan
Habitat 2,750–4,250 m
RHS Hardiness Rating H5
Awards AM 1932 (L. de Rothschild, Exbury) as R.timetum; flowers rosy purple. AM 1935 (J.J. Crosfield, Embley Park, Hants) as R. siderophylloides; flowers bright pinkish mauve, with darker spots. AM 1937 (L. de Rothschild, Exbury) as R. exquisitum, from Forrest 20489; flowers light mauve pink, spotted red. AM 1990 (P.A. Cox, Glendoick) to a clone 'Pentland'; trusses compound, containing up to 21 flowers, corolla purple, paling in throat, with sparse green and red-brown spotting in upper throat.
Conservation status Least concern (LC)
Taxonomic note This is a distinctive species, with no close allies. Royal Horticultural Society (1997)
An evergreen shrub or small tree. Leaves elliptic, oblong-elliptic to roundish, 1 to 31⁄2 in. long, 3⁄4 to almost 2 in. wide, obtuse to rounded at the apex, broad-cuneate or rounded or slightly cordate at the base, green or grey-green above, sparsely to densely scaly and more or less glaucous beneath (brownish in densely scaly forms), both sides glabrous except for occasional down on the midrib above; stalk up to 5⁄8 in. long. Flowers three to eleven in a terminal truss (occasionally also produced from the upper leaf-axils), opening in April or May; flower-stalks up to 11⁄8 in. long. Calyx small, shallowly lobed. Corolla funnel-shaped or sometimes inclining to bell-shaped, five-lobed, 2 to 21⁄2 in. across, in some shade of rosy pink or purplish pink, unspotted or with markings of crimson or reddish brown. Stamens ten, hairy towards the base. Ovary densely scaly; style glabrous. Bot. Mag., tt. 8784, 9597. (s. Triflorum ss. Yunnanense)
R. oreotrephes has a wide range in the Sino-Himakyan region, from S.W. Szechwan westward through N.W. Yunnan and upper Burma to S.E. Tibet, where it extends as far as the region of the Tsangpo bend, occurring at altitudes of mostly 9,000 to 13,000 ft, in open thickets and scrub, or as undergrowth in pine woodland. It was introduced by Forrest in 1910 from the Lichiang range, Yunnan, and described from a specimen he collected there; later he sent seeds on many occasions, as also did Kingdon Ward and Rock. It is a somewhat variable species, though less so than is suggested by the numerous synonymous names, which are founded on minor fluctuations. The plants originally grown as R. oreotrephes, i.e., the species in its old and narrower sense, are themselves far from uniform. The flower-colour ranges from pearly grey lavender to deep rosy lavender; the foliage is more or less glaucous, especially on the undersides, and on some plants it is very noticeable even on the upper surface of the young leaves – J. C. Williams compared the best forms in this respect to the sea-holly. Harry White raised a fine garden race at the Sunningdale Nurseries by crossing his two best forms of R. oreotrephes (Y.B. Rhod. Ass. 1939, p. 30).
Of the species now included in R. oreotrephes, Lionel de Rothschild most admired R. exquisitum, described from a plant growing at Exbury which had been raised at the Sunningdale Nurseries from F.20489, collected in S.W. Szechwan (see further below under awards).
R. oreotrephes is perfectly hardy, though in cold gardens it may lose most of its leaves in winter; usually it does not flower until May, so the display is not often spoilt by frost. Lionel de Rothschild found at Exbury that R. oreotrephes (at least in the old sense) resents being moved, and Mr Cox confirms this from his experience at Glendoick; so it is best put in when young.
The following forms of R. oreotrephes have received the Award of Merit: May 24, 1932, shown from Exbury as R. timeteum, raised from Rock 59593, flowers rosy purple; May 21, 1935, as R. siderophylloides, shown by J. J. Crosfield, Embley Park, Hants, bright pinkish mauve flowers, spotted within, leaves bright green above; May 25, 1937, as R. exquisitum, shown from Exbury, flowers light mauvish pink with some crimson speckling.
cv. ‘Exquisitum’. – Although R. exquisitum Hutch. is certainly synonymous with R. oreotrephes, the name is founded on a cultivated plant raised from F. 20489, which had larger flowers and leaves than normal. Mr Davidian suggests that the cultivar name ‘Exquisitum’ should be used to distinguish the clone deriving from this plant (A.M. to Exbury, 1937).