An evergreen shrub up to 9 ft high in the wild, forming a rounded bush in cultivation as wide as it is high; young shoots usually clothed at first with stalked glands. Leaves round to roundish ovate, the base truncate, rounded or heart-shaped, the apex with a short mucro, 1 to 3 in. long, usually not quite so wide, dark glossy green and with scattered hairs above, glaucous beneath with glands on the midrib and margin; stalk 3⁄8 to 1 in. long, usually very glandular. Flowers opening during April and May in a terminal truss of five to eight flowers. Calyx very small with shallow triangular lobes, glandular like the flower-stalk which is 3⁄4 in. long. Corolla openly bell-shaped, five-lobed, 11⁄2 in. long and wide, pale or deep rose with a blotch of intense crimson at the base, lobes notched. Stamens ten, their white stalks from 1⁄2 to 1 in. long, glabrous except for (occasionally) a few minute hairs at the base; anthers brown. Ovary covered with red glands, of which a few extend a short way up the style. Bot. Mag., t. 8789. (s. Thomsonii ss. Campylocarpum)
Native of W. Yunnan and N.E. upper Burma; found by Forrest on the Shweli-Salween divide and introduced by him in 1912; later sendings are from farther north on the E. Irrawaddy-Salween divide and the Tali range. R. callimorphum is a very pretty species of neat habit. It is variable in flowering-time, which is mid- to late May or even early June in some forms. It is hardy at Kew when given a sheltered place and some shade.
R. myiagrum Balf. f. & Forr. – This differs from R. callimorphum in its flowers being white; they are bell-shaped and 11⁄4 to 11⁄2 in. wide. Leaves nearly orbicular, 1 to 2 in. long. The specific name, meaning 'fly-catcher', applies to the flower-stalks, which are furnished with such viscid glands that small flies are caught thereon in great numbers. Forrest's specimens, collected wild in W. Yunnan, are covered with them. Introduced in 1919. Flowers in May and June. It has a restricted distribution near the borders between N.W. Yunnan and Burma and is really no more than a white-flowered form of R. callimorphum.
From the Supplement (Vol. V)
var. myiagrum (Balf. f. & Forr.) Chamberlain R. myiagrum Balf.f. & Forr. – This differs from typical R. callimorphum only in its white flowers. Stalked glands on the pedicels are also a feature of typical R. callimorphum.