Kindly sponsored by
Peter Norris, enabling the use of The Rhododendron Handbook 1998
Article from Bean's Trees and Shrubs Hardy in the British Isles
'Rhododendron lacteum' from the website Trees and Shrubs Online (treesandshrubsonline.
Shrub or small tree, 2–7.5 m. Leaves 8–17 × 4.5–7 cm, elliptic to obovate, apex rounded, apiculate, lower surface covered with a thin one-layered compacted indumentum composed of grey-brown radiate hairs; petioles glabrescent. Flowers 15–30, in a dense truss; calyx c.1 mm; corolla pure yellow, without flecks though a purple blotch is sometimes present, widely campanulate, nectar pouches lacking, 40–50 mm; ovary densely tomentose, style glabrous. Flowering April-May. Royal Horticultural Society (1997)
Distribution China W & N Yunnan
Habitat 3,700–4,000 m
RHS Hardiness Rating H5
Awards FCC 1926 (A.M. Williams, Werrington Park, Cornwall); flowers Sulphur White, with a dark crimson blotch. FCC 1965 (S.F. Christie, Blackhills, Elgin) to a clone 'Blackhills'; flowers yellow, without a blotch or spots.
Conservation status Near threatened (NT)
Taxonomic note A distinctive species on account of its yellow flowers and stellate indumentum. In cultivation there are forms with a pink flush to the corolla. These may be hybrids with R. cyanocarpum. Royal Horticultural Society (1997)
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).
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.