14. Rhododendron austrinum (Small) Rehder in L. H. Bailey, Stand. Cycl. Hort. 6: 3571. 1917.
Azalea austrina Small, Fl. S.E. U.S. ed. 2, 1356. 1913
Shrubs or trees, to 3(-5) m, usually not rhizomatous. Stems: bark smooth to vertically furrowed, shredding; twigs conspicuously multicellular stipitate-glandular-hairy, otherwise ± moderately to densely unicellular-hairy. Leaves deciduous; petiole multicellular stipitate-glandular-hairy and unicellular-hairy; blade ovate to obovate, 3-11 × 1.5-4.5 cm, thin, membranous, margins entire, plane, ciliate, eglandular- and stipitate-glandular-hairy, apex acute to obtuse, often mucronate, abaxial surface ± moderately unicellular-hairy, adaxial surface sparsely scattered stipitate-glandular-hairy, otherwise ± moderately unicellular-hairy, rarely glabrescent. Floral bud scales densely to moderately unicellular-hairy abaxially, margins unicellular-ciliate, also partly glandular-serrate. Inflorescences 9-24-flowered; bracts similar to bud scales. Pedicels 5-17 mm, stipitate-glandular-hairy, otherwise ± densely unicellular-hairy. Flowers opening before or with leaves, erect to horizontal, slightly or not fragrant; calyx lobes 0.5-2.5 mm, scattered stipitate-glandular-hairy, otherwise unicellular-hairy, margins long stipitate-glandular-hairy; corolla yellow to orange, with usually red or orange-red tube, with indistinct, darker yellow, orange, or red blotch on upper lobe, funnelform, 25-45 mm, scattered stipitate-glandular-hairy, otherwise ± moderately unicellular-hairy on outer surface, petals connate, lobes 9-20 mm, tube ± gradually expanded into lobes, 15-25 mm (longer than lobes); stamens 5, much exserted, ± unequal, 52-77 mm. Capsules borne on erect pedicels, 14-26 × 3-5.5 mm, sparsely to densely stipitate-glandular-hairy, otherwise moderately to densely unicellular-hairy. Seeds without distinct tails, flattened portion of testa well developed at each end; testa expanded, dorsiventrally flattened, ± loose. 2n = 26.
Flowering spring. Wooded slopes, bluffs or lowlands along streams; 0-100 m; Ala., Fla., Ga., Miss.
Rhododendron austrinum is most closely related to R. luteum Sweet of eastern Europe, Turkey, and the Caucasus region and to R. occidentale (K. A. Kron 1993).