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').
From the Supplement (Vol. V)
Included in R. mekongense (see this supplement, under R. trichocladum).