An evergreen shrub or tree, occasionally 30 ft high in the wild; young shoots at first floccose-hairy and glandular, becoming glabrous. Leaves oblong-lanceolate, 21⁄2 to 5 in. long, 3⁄4 to 11⁄2 in. wide, abruptly narrowed at the apex to a sharp, horny point, base truncate or rounded, dull green and glabrous above, paler and glossy beneath, with traces of flock and glands on the prominent midrib, otherwise glabrous; petiole 1⁄2 to 1 in. long, with the same covering as the midrib. Flowers ten to fifteen, borne in April or May in a loose terminal truss; rachis about 3⁄4 in. long; pedicels 1 to 11⁄2 in. long, slightly glandular-hairy. Calyx minute, fringed with glands. Corolla five-lobed, widely campanulate, up to 2 in. long and wide, white or pale pink, usually with rich red speckling merging into a blotch at the base, but in some forms the markings are less pronounced. Stamens finely downy at the base. Ovary clad with short, spreading, usually gland-tipped hairs, but sometimes the hairs are eglandular; style glandular at the base or eglandular. Bot. Mag., n.s., t. 517. (s. Barbatum ss. Maculiferum)
Native of Formosa, where, according to Wilson, it is the common rhododendron of the forests above 6,500 ft; he introduced it in 1918, from Mt Arisan. It is perfectly hardy in a sheltered place, and very beautiful in its flowers, especially when these are speckled and blotched with clear red. It appears to be correctly placed in the Maculiferum subseries of Barbatum, where its nearest Chinese ally is R. pachytrichum. It received an Award of Merit when shown by Capt. Collingwood Ingram, Benenden, Kent, on May 1, 1956.
R. anhweiense Wils. – This species was discovered in 1923 in southern Anhwei, China, and described from fruiting specimens (as R. “anwheiense”, an orthographic error); it was again collected in fruit two years later. It appears to be allied to R. morii, though the leaves are remarkably small, only 2 in. or so long on wild plants, 3 in. long on cultivated plants, which have white, sparsely or densely speckled flowers borne in April or May in trusses of about ten; corolla campanulate, 13⁄8 to 2 in. wide. It is hardy, but only the forms with conspicuously speckled corollas are worth growing.
From the Supplement (Vol. V)
R. anhweiense, mentioned under this, is transferred to R. maculiferum as a subspecies in the Edinburgh revision.
R. pachysanthum Hayata was given as a synonym of R. morii, this being the position assigned to it by Tagg in Species of Rhododendron and by Li in Woody Flora of Taiwan. It has usually been considered as a state of R. morii with a completely glabrous style and a more persistent leaf indumentum. However, it is possibly a distinct species (Rev. 2, p. 274). Plants under the name R. pachysanthum are in cultivation from seeds collected by John Patrick in 1972 and are very ornamental in flower and foliage.