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 ambiguum' from the website Trees and Shrubs Online (treesandshrubsonline.
Shrub, 1.5–5 m; young shoots glabrous. Leaves 3–6(–8) × 1.5–3.2 cm, narrowly ovate to narrowly elliptic, apex acute, upper surface pubescent for a short distance along midrib, otherwise glabrous, lower surface covered with large dark brown broadly rimmed touching or overlapping scales, midrib pubescent towards base. Flowers 3(–5), in a loose terminal inflorescence; calyx obscurely lobed, sometimes ciliate; corolla yellow, often with greenish or darker yellow spots on upper lobes, openly funnel-shaped, strongly zygomorphic, 20–26 mm, outer surface usually scaly, otherwise glabrous; stamens 10; ovary scaly impressed below the decimate style that is usually glabrous (rarely puberulent) at base. Flowering April-May Royal Horticultural Society (1997).
Distribution China C Sichuan, Guizhou
Habitat 2,600–4,500 m
Awards AM 1976 (W.L. & R.A. Banks, Hergest Croft, Kington) to a clone 'Jane Banks'; flowers yellow-green, with greenish spots.
Conservation status Least concern (LC)
Taxonomic note Superficially similar to R. triflorum but differing in its bark, the larger, denser scales, and the lack of indumentum on the corolla Royal Horticultural Society (1997).
An evergreen shrub up to 15 ft high in the wild, with a rough bark; young shoots covered with pale yellow, glistening scales. Leaves aromatic, oval, sometimes slightly obovate or ovate, 11⁄2 to 3 in. long, 5⁄8 to 11⁄4 in. wide, scattered along the shoot, pointed, rounded or slightly heart-shaped at the base, dark green and somewhat scaly above, downy along the midrib, paler and much more scaly beneath, the scales large, some yellowish brown, others dark brown or black; stalk 1⁄4 to 5⁄8 in. long. Flowers produced in April or May in terminal trusses of five to six. Calyx minute, scaly. Corolla pale yellow with yellow-green spots on the upper lobes, about 2 in. wide, broadly funnel-shaped, slightly scaly outside. Stamens ten, whitish, hairy near the base. Ovary scaly; style glabrous. Bot. Mag., t. 8400. (s. and ss. Triflorum)
R. ambiguum is abundant in W. Szechwan, China, whence it was introduced by Wilson in 1904. It is a species of little ornamental value, allied to the Himalayan R. triflorum, but in that species the leaves are glabrous on the midrib above, and the scales on the underside are very small, widely spaced (more than their own diameter apart) and equally coloured (Davidian, R.C.Y.B. 1963, pp. 172, 174).