An evergreen shrub or a tree up to 30 ft high; young shoots 1⁄2 in. thick, at first scurfy, becoming glabrous. Leaves oblong-ovate, shortly pointed, rounded or slightly heart-shaped at the base; 4 to 8 in. long, about half as much wide; dark green and glabrous above, clothed beneath with a fine, close tawny felt, much of which sometimes wears off before the leaf falls; stalk 3⁄4 to 11⁄2 in. long. Flowers opening in April, closely packed twenty or thirty together in a truss up to 8 in. across, on downy stalks up to 1 in. long. Calyx a mere wavy rim. Corolla bell-shaped, soft or canary yellow, 2 in. wide, five-lobed, not markedly blotched. Stamens ten, downy towards the base. Ovary covered with whitish down; style glabrous. Bot. Mag., t. 8988. (s. Lacteum)
R. lacteum was discovered by the French missionary Delavay near Hoking, Yunnan, in 1884, forming almost pure forests on Mt Koua La Po at 9,500 to 12,500 ft; it was introduced by Forrest from the Tali range, some seventy-five miles farther south, in 1910 (F.6778, with canary-yellow flowers). Subsequently he sent seeds from the Chienchuan-Mekong and Salween-Irrawaddy divides, but some of these were from plants with pale yellow or even white flowers.
Unfortunately, R. lacteum is not easy to grow and many once-famous plants are now dead. It is also a shy seeder and difficult to increase by layering, consequently very rare in gardens. It is said to grow best in a very acid soil.
R. lacteum was awarded a First Class Certificate on April 13, 1967, when shown by S. F. Christie from his garden at Blackhills, Morayshire (clone 'Blackhills'). The plant there, about 15 ft high, bears primrose-yellow flowers, without spot or blotch (R.C.Y.B. 1968, p. 25 and Frontispiece). There are some fine plants at Corsock, Galloway, raised from seeds collected by Forrest during his last expedition, one 20 ft high and wide (R.C.Y.B. 1965, pp. 50-1 and Plate 2).
From the Supplement (Vol. V)
It is welcome news that this species was reintroduced in 1981 by the Sino-British Expedition to the Cangshan (Tali range), the area where Forrest first collected seed in 1910. It is now placed in subsect. Taliensia, which includes the former Lacteum series.