A deciduous bush, of rounded habit, 4 to 8 ft high, with stiff, erect branches; young shoots sparsely hairy. Leaves narrowly oval or obovate, 2 to 4 in. long, 3⁄4 to 11⁄4 in. wide; dark green and sparsely hairy above, more or less glaucous and slightly hairy beneath when young, especially on the midrib and margins. Flowers six to ten in a cluster, produced during May on the end of leafless shoots, the corolla being of various shades of soft rose, salmon-red, and orange-red, 21⁄2 to 31⁄2 in. wide, the lobes oblong; calyx-lobes oblong to linear-oblong, as long as the ovary, conspicuously edged with long whitish hairs; flower-stalk 1⁄2 to 1 in. long, hairy. Bot. Mag., t. 5905 (s. Azalea ss. Luteum)
Native of the main island of Japan and of Hokkaido, in open grassland and scrub, never in woods or dense thickets (Wilson); introduced to the Continent in 183o(?) and to Britain in the 1860s. It was taken up by the Ghent nurserymen, who used to raise it in large quantities from seed, mainly for forcing, and in that way many colour variants came to be selected, some of which come true from seed if self-pollinated. See further in the section on hybrids, under Mollis Azaleas, under which it is customary to group the named selections of R. japonicum as well as the hybrids between it and the closely allied R. molle (sinense), q.v.