21. Rhododendron prunifolium (Small) Millais, Rhododendrons. 230. 1917.
Plumleaf azalea Plumleaf azalea
Azalea prunifolia Small, Fl. SE. U.S. ed. 2, 1356, 1375. 1913
Shrubs or trees, to 5(-6) m, usually not rhizomatous. Stems: bark smooth to vertically furrowed, shredding; twigs glabrous. Leaves deciduous; petiole usually multicellular eglandular-hairy and unicellular-hairy; blade ovate to obovate, 3-11(-15.2) × 1-4(-5) cm, thin, membranous to chartaceous, margins entire, plane, ciliate, eglandular-hairy, apex acute to obtuse, often mucronate, abaxial surface glabrous, adaxial surface glabrous or, rarely, sparsely scattered eglandular-hairy. Floral bud scales glabrous abaxially, margins unicellular-ciliate. Inflorescences 4-7-flowered; bracts similar to bud scales. Pedicels 5-12 mm, eglandular-hairy. Flowers opening after development of leaves, erect to horizontal, not fragrant; calyx lobes 1-3(-4) mm, glabrous or sparsely unicellular-hairy, margins eglandular-hairy; corolla red to orange-red or orange, with indistinct darker blotch on upper lobe, funnelform, 36-53 mm, glabrous or very sparsely long stipitate-glandular-hairy, sometimes also sparsely unicellular-hairy on outer surface, petals connate, lobes 11-22 mm, tube abruptly expanded into lobes, 23-35 mm (± equaling or much longer than lobes); stamens 5, much exserted, ± unequal, 64-84 mm. Capsules borne on erect pedicels, 15-22 × 4.5-7 mm, densely, stiffly eglandular-hairy and sparsely unicellular-hairy. Seeds without distinct tails, flattened portion of testa well developed at each end; testa expanded, dorsiventrally flattened, ± loose. 2n = 26.
Flowering summer. Shady forests, especially ravines along streams; of conservation concern; 30-200 m; Ala., Ga.
Rhododendron prunifolium is most closely related to R. flammeum, R. cumberlandense, and R. calendulaceum, and can be distinguished from all of those orange- to red-flowered species by its nearly glabrous and more gradually expanded corolla tube and by the indistinct nature of the floral blotch (K. A. Kron 1993). This species is federally protected.