An evergreen shrub 10 to 14 ft high; young shoots glabrous. Leaves oval-oblong, rounded at both ends with a short mucro at the apex, 3 to 5 in. long, about half as much wide, green and glabrous above, rather glaucous beneath and glabrous except along the veins upon which, at fairly regular intervals, occur little tufts of down; stalk up to 11⁄8 in. long. Flowers produced in late March or April ten to fifteen in a truss, on stalks up to 1 in. long. Calyx cup-shaped, up to 7⁄8 in. long. Corolla blood-red sometimes pink, bell-shaped, 11⁄2 to 2 in. wide, five-lobed, the lobes rounded and deeply notched in the middle; stamens ten, quite glabrous; ovary and style glabrous, the latter longer than the stamens but shorter than the corolla. Bot. Mag., t. 4926. (s. and ss. Thomsonii)
Native of the Himalaya from Bhutan eastward, and of the Mishmi Hills; discovered by Booth in 1849 in an outer range just east of the Bhutan frontier, and introduced by him. For many years this handsome and richly coloured species was one of the rarest of rhododendrons; even now, although it is becoming more widely spread in gardens, it is still quite uncommon. It is related to R. thomsonii, but is well distinguished from that and all other known rhododendrons by the curious tufts of down scattered along the chief veins beneath the leaf, and nowhere else. It is grown out-of-doors, really successfully, in the southern and western maritime counties only, although 30 or 40 miles south of London it has survived pretty severe winters. In view of this tenderness it is interesting to note Booth's record that, when and where he first collected it, frost and snow were very severe and continuous; also that it is associated in the wild with Pinus wallichiana, a perfectly hardy pine.
A hardier form of R. hookeri was introduced by Kingdon Ward in 1938 from the Poshing La in the Assam Himalaya.
R. hookeri was awarded a First Class Certificate when shown from Bodnant on March 21, 1933.
From the Supplement (Vol. V)
† R. subansiriense Chamberlain & Cox – Near to R. hookeri (and also to R. hylaeum and R. faucium), but differing from all these in the tomentose, glandular ovaries. Flowers scarlet as in R. hookeri, which it also resembles in its smooth, peeling bark. Discovered by Cox and Hutchison in the Apa Tani valley of the Assam Himalaya in 1965 and introduced by them. See further in Notes Roy. Bot. Gard. Edin., Vol. 36, p. 124 (1978).