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Small shrub, 0.3-1.5 m; young shoots scaly, setose, sometimes also puberulous. Leaves evergreen, 2.3-6.7 x 1.3-3 cm, obovate, to elliptic, usually lacking setae, though occasionally with midrib puberulent or with a few setae, lower surface pale green, covered with large to medium-sized scales, 1-3× their own diameter apart. Flowers 3-6, in a loose inflorescence; calyx small; corolla yellowish green, yellow or reddish yellow, funnel-campanulate, zygomorphic, 15-25 mm; stamens 10; ovary densely scaly, style straight or sharply bent. Flowering May-June. Royal Horticultural Society (1997)
Distribution China S Tibet
Habitat 2,850-3,300 m
RHS Hardiness Rating H5
Awards AM 1972 (E.H.M. and P.A. Cox, Perth) to a clone 'Doshong La', from Kingdon-Ward 5829; flowers yellow, flushed rose at corolla lobe tip externally, with Olive Green flecking.
Conservation status Vulnerable (VU)
Taxonomic note Recent field observations (P. & K. Cox) have confirmed the distinctness of this species. It may be distinguished from the closely allied R. mekongense by its evergreen leaves. Royal Horticultural Society (1997)
An evergreen shrub up to 6 ft high in cultivation; young stems bristly at first. Leaves broad-elliptic, obovate or oblong-obovate, up to 17⁄8 in. long and 1 in. wide, rounded at the apex, rounded-truncate at the base, glaucous when young, upper side pale sea-green on mature leaves, glabrous, underside paler, sparsely scaly, margins and petioles bristly at first, later almost glabrous; petioles up to 1⁄4 in. long. Flowers opening in June, borne in terminal trusses of four or five; pedicels 1⁄2 to 5⁄8 in. long, bristly and scaly. Calyx with ovate to roundish lobes, about 1⁄12 in. long, bristly and scaly. Corolla five-lobed, broadly funnel-shaped, about 11⁄2 in. wide, yellowish green or lemon-yellow, sometimes tinged with red on the margin, the upper lobes marked with green spots, sparsely scaly outside. Stamens ten, the upper five about half as long as the lower set. Ovary densely scaly; style curved, glabrous, (s. Trichocladum)
R. viridescens was described in 1933 from a plant at Exbury, raised from Kingdon Ward’s 5829, collected on the Doshong La at the eastern end of the Himalaya. The seed under this number was distributed as R. trichocladum, to which R. viridescens is closely allied, though it differs horticulturally in its persistent leaves and late-flowering. The wild-collected specimens and some from cultivated plants have the pedicels, leaf undersurface, and petioles hairy, but in the type and in some garden plants, the hairs are less evident or lacking. It is quite an attractive species both in flower and foliage, and received an Award of Merit when shown by E. H. M. and P. A. Cox, Glendoick Gardens Ltd, Perth, on June 27, 1972 (clone ‘Doshong La’).
Included in R. mekongense (see this supplement, under R. trichocladum).