An evergreen tree up to 25 ft high in nature, mostly seen in cultivation as a shrub of stiff, rather gaunt habit; young shoots, leaf-stalks, and flower-stalks all glandular-bristly. Leaves narrowly oblong, often inclined to oblanceolate, rather abruptly narrowed at the apex to a slender point; tapered, rounded, or slightly heart-shaped at the base, 6 to 12 in. long, 11⁄2 to 3 in. wide, dark green or yellowish green and eventually glabrous above, pale green beneath and more or less furnished all over with bristly down, but especially on the midrib. Flowers borne during May in trusses 5 or 6 in. across, of up to fifteen or more, on stalks up to 11⁄2 in. long. Calyx deeply five-lobed, the lobes 3⁄8 in. long, oblong, blunt, bristly. Corolla bell-shaped, five-lobed, 2 in. wide, varying in colour from a dull magenta-pink to a purplish rose with a dark blotch at the base. Stamens ten, 1 to 11⁄4 in. long, glandular-downy towards the base. Ovary and base of style clothed with white bristles. Bot. Mag., t. 9035. (s. Barbatum ss. Glischrum)
R. glischrum was discovered by Forrest on the Kari pass, Mekong-Salween divide in 1914, and was introduced from there. Subsequently it was collected over a wide area from here westward to the eastern end of the Himalaya. The type specimens bore only withered flowers, but Forrest noted the colour of his later findings as 'plum-purple', 'clear rose', or 'white flushed rose'. In cultivation, many of the plants raised from the wild seeds had flowers of an unpleasant magenta shade, but in the best forms, which may be the minority, they are clear red in the bud, opening rosy pink or rosy lilac. R. glischrum is hardy in woodland near London, but is probably best suited in the rainier parts of the country. It is, in any case, rarely seen outside collections.
var. adenosum Cowan & Davidian – Calyx shorter than in the type. Leaves somewhat smaller, with short bristly glands on the underside. Described from Dr Rock's 18228, collected in S.W. Szechwan and in cultivation at Edinburgh from his seed-number 03837.
R. glischroides Tagg & Forr. – This species, perhaps no more than a local variety of R. glischrum, is known from a comparatively small area on the Irrawaddy-Salween divide, within the range of R. glischrum itself. The main botanical distinction is that the veins on the leaf-undersides are clothed with fine hairs as well as bristles. But as seen in cultivation it is a finer species, the leaves dark green with impressed veins and the flowers white more or less flushed with pink. It was found and introduced by Forrest.
Two other relatives of R. glischrum, neither of much importance, may be mentioned here:
R. rude Tagg & Forr. – This differs from R. glischrum in the relatively broader leaves, up to 71⁄2 in. long, 3 in. wide, covered on the upper surface as well as beneath with gland-tipped bristly hairs. The flowers are smaller and are sometimes barred with pink on the outside. It was found in the same area as R. glischroides and was introduced by Forrest under F.25645.
R. vesiculiferum Tagg – Leaves thinner than in R. glischrum, more rugose, with bladder-like hairs along the midrib and main veins in addition to the normal simple hairs. It was discovered by Kingdon Ward in the Seinghku valley N.W. upper Burma and introduced by him (KW 6856; flowers 'in large trusses, pinkish purple, splashed with dusky purple at the base.'). He later reintroduced it from the Adung valley a short way to the east, where the flowers vary in colour from white to deep rose. The clone 'High Flier' received an Award of Merit on April 30, 1968, when shown by the Crown Estate Commissioners, Windsor Great Park.
From the Supplement (Vol. V)
The var. adenosum has been raised to species rank; see below. The species mentioned under R. glischrum on page 673 are disposed of as follows in the Edinburgh revision:
subsp. glischroides (Tagg & Forr.) Chamberlain R. glischroides Tagg & Forr.
subsp. rude (Tagg & Forr.) Chamberlain R. rude Tagg & Forr.
R. vesiculiferum – Accepted as a distinct species.
R. adenosum (Cowan & Davidian) Davidian R. glischrum var. adenosum Cowan & Davidian; R. kuluense Chamberlain – Although allied to R. glischrum, this is distinct from it in foliage and occupies a separate area to the east of it (Rev. 2, p. 284).