An evergreen shrub 10 to 25 ft high; young shoots and leaves quite glabrous. Leaves elliptic-oblong, rounded or rather heart-shaped at the base, bluntish at the apex, as much as 12 in. long by 4 in. wide, usually smaller, lightish green above, rather glaucous beneath; stalk 1 to 13⁄4 in. long. Flowers rather fragrant, opening in late June or July in trusses of seven to ten. Corolla seven-lobed, 4 to 5 in. across, funnel-shaped at the base, white or faintly rose-tinted, greenish and downy inside the tube at the base. Stamens eighteen or twenty, downy at the base; ovary and style glandular from top to bottom. Bot. Mag., t. 9524 (s. and ss. Fortunei)
R. diaprepes was found by Forrest in 1913 on the Shweli-Salween divide, Yunnan, near the border with Burma, at 9,000 ft. It was introduced by him from the same area in the same year (F.11958). Both in leaf and flower this is the finest of the Fortunei subseries, the latter exceeding even the flower of R. discolor in size. It scarcely differs from R. decorum in essential botanical detail, but grows in a warmer and moister region, and is better suited for the maritime parts of the south and west of Britain. But it seems to be little cultivated at the present time and is best known as a parent of the hybrid Polar Bear, which flowers at the same time and is much hardier. It received an Award of Merit when shown by Lionel de Rothschild from Exbury on June 29, 1926.
cv. 'Gargantua'. – A triploid plant with larger flowers and leaves than normal, raised from F.11958. Award of Merit June 23, 1953.