An evergreen, low shrub, usually under 3 ft in height, with slightly downy young shoots. Leaves sometimes rather leathery, glabrous and dark green above, more or less clothed with brownish-red felt beneath; narrowly oval or slightly obovate, 2 to 4 in. long, 3⁄4 to 11⁄2 in. wide; stalk stout, 1⁄4 in. long. Flowers yellowish white or pink-tinged, spotted in the upper part of the throat, borne in May in candelabroid trusses; bud-scales slow to fall. Corolla 2 in. wide, funnel-campanulate, wavy-edged; stamens ten; calyx very small; flower-stalk slightly downy, about 11⁄2 in. long; seed-pods erect. Bot. Mag., tt. 1145 and 3422. (s. Ponticum ss. Caucasicum)
Native of the Caucasus, Russian Armenia, and north-eastern Asiatic Turkey, forming a dense scrub at or above the timber-line; introduced in 1803. Although its hybrid progeny is numerous in gardens, the true species is itself now scarcely ever seen. It is an interesting dwarf bush, remarkable for its dense habit and slow growth. Since it approaches 9,000 ft in the wild it is perfectly hardy in this country and flowers when quite young. It was reintroduced by Apold, Cox, and Hutchison from Turkey in 1962 (R.C.Y.B. 1963, pp. 66-7).
R. caucasicum is the parent of many hardy, early-flowering hybrids, of which the best-known are the crosses with R. arboreum and their offspring (grex Nobleanum). Others are of more complex origin. Some of these hybrids show the influence of R. caucasicum in their erect, clustered peduncles and persistent bud-scales. In some the finely impressed venation of the leaf of R. caucasicum is also evident.
R. aureum Georgi R. chrysanthum Pall. – This species is related to R. caucasicum, differing in the always yellow flowers and the smaller, glabrous, strongly net-veined leaves. It is a dwarf, slow-growing shrub with a wide distribution in the mountains of northern Asia, from the Altai to the Russian Far East and Korea; it also ranges south through Sakhalin to central Japan. Probably the present garden stock is of Japanese provenance, though the species was introduced from Russia in 1796. It is not an easy species and scarcely worth growing in Britain.
R. nikomontanum Nakai, found wild in Japan, is supposed to be a natural hybrid between R. aureum and R. brachycarpum.