A deciduous shrub up to 10 or more feet high; young shoots bristly-hairy. Leaves obovate or oval, 2 to 4 in. long, 3⁄4 to 11⁄4 in. wide, with a few scattered hairs above, downy beneath, especially on the midrib and veins; leaf-stalk hairy, very short. Flowers of various shades of red, orange, and yellow, scarcely fragrant, produced in showy terminal clusters of five or more. Corolla-tube about 1⁄2 in. long, glandular-hairy; lobes often 1 in. long, often considerably longer than the tube; calyx-lobes edged with long, erect hairs; flower-stalk 1⁄4 in. long, glandular-hairy. Flowers in May or early June. (s. Azalea ss. Luteum)
Native of eastern N. America in the Alleghenies. This is the most brilliantly coloured of all wild azaleas, and is the source of the scarlet and orange-coloured garden hybrids. Bartram gives this description of his first sight of this azalea in the Carolina mountains: 'I saw the blossoms covering plants on the hill-sides in such incredible profusion that, suddenly opening to view from deep shade, I was alarmed by the apprehension of the hill being on fire.'
R. calendulaceum was brought to England by John Lyon in 1806, but there may have been an earlier introduction, since the azalea named A. aurantiaca by Dietrich in 1803 came from England and was probably a form of this species.
A.M. 1965 to clone 'Burning Light', shown by the Crown Estate Commissioners.
R. bakeri (Lemmon & McKay) Hume Azalea bakeri Lemmon & McKay; R. cumberlandense E. L. Braun – Allied to R. calendulaceum, but flowering about three weeks later and generally of dwarfer, more compact habit, rarely up to 9 ft high; said to be superior as an ornamental. Native mainly of the Cumberland plateau. See further in R.C.Y.B. 1957, pp. 20-1, 23.