in L. H. Bailey, Stand. Cycl. Hort. 6: 3571. 1917 ,.
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.
Phenology: Flowering spring.
Habitat: Wooded slopes, bluffs or lowlands along streams
Elevation: 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).