A deciduous azalea, described as often tree-like in habit in the wild, 3 to 15 ft high (Wilson); young shoots clothed with forward-pointing hairs, becoming brown and nearly glabrous the second year. Leaves obovate, ovate, or diamond-shaped, usually acutely pointed; distributed along vigorous shoots but often produced in a whorl at the end of shorter twigs, 11⁄2 to 31⁄2 in. long, 1 to 21⁄4 in. wide, pale green and soon glabrous above, greyer green and rather conspicuously veined beneath; stalk 1⁄4 to 1⁄2 in. long, downy only when young. Flowers produced two to four together in a terminal cluster. Calyx very small, hairy. Corolla about 2 in. wide, of a rather dull rich red, funnel-shaped at the base, with five spreading lobes. Stamens six to ten, usually glabrous. Ovary densely clothed with erect, pale, reddish hairs; style usually glabrous. Bot. Mag., t. 9475. (s. Azalea ss. Schlippenbachii)
Native of S. Japan, in Kyushu, Shikoku, and the Kinki district of the main island; also of the Korean island of Quelpaert; introduced by Wilson in 1914 to the Arnold Arboretum. Plants raised from seed obtained from that institution in 1915 flowered in May 1921 at Kew, where the species has proved fairly hardy in a sheltered place. It is most nearly akin to R. reticulatum, but is well marked by the colour of the flowers which may be termed rich brick-red and as distinct among azaleas as that of R. griersonianum is among rhododendrons proper.
R. amagianum (Makino) Makino ex Nemoto Azalea amagiana Makino – Closely related to R. weyrichii, but with thicker leaves, lustrous above, the base of the midrib beneath and the petiole white-tomentose; they are commonly rhombic in outline and relatively rather broader than in R. weyrichii. The flowers are often more than 2 in. wide and are borne in July after the leaves have expanded. Bot. Mag., n.s., t. 379. It is a local species, confined to Mt Amagi and Mt Hijane in Idzu province; introduced to Britain in the late 1930s. It is hardy but needs light shade at least in southern England. A mature specimen of this azalea is a wonderful sight when in flower. The colour is a soft shade of true scarlet, with darker spotting on the upper lobe. Award of Merit July 6, 1948, when shown by Lord Aberconway, Bodnant.
R. sanctum Nakai – This, another native of Japan, is very closely allied to R. amagianum, but the flowers are rose-coloured and are borne earlier, in May or June. Like R. amagianum it is a local species, found wild only in the mountains south-east and south-west of Nagoya.