19. Rhododendron canescens (Michaux) Sweet, Hort. Brit. (ed. 2). 343. 1830.
Piedmont or southern pinxterbloom azalea
Azalea canescens Michaux, Fl. Bor.-Amer. 1: 150. 1803; A. candida Small
Shrubs or trees, to 6 m, usually not rhizomatous. Stems: bark smooth to vertically furrowed, shredding; twigs scattered, multicellular eglandular- and/or stipitate-glandular-hairy (hairs unbranched), otherwise moderately to densely unicellular-hairy. Leaves deciduous; petiole usually multicellular eglandular- or stipitate-glandular-hairy, also unicellular-hairy; blade ovate to obovate, 2.5-10(-13) × 1.2-3(-4) cm, thin, membranous to chartaceous, margins entire, rarely minutely serrulate, plane, inconspicuously ciliate, eglandular-hairy (hairs appressed to margins), apex acute to obtuse, often mucronate, abaxial surface densely to sparsely unicellular-hairy, sometimes glabrous or glabrate, often also scattered eglandular-hairy, adaxial surface usually scattered eglandular-hairy, otherwise sparsely unicellular-hairy, sometimes glabrous. Floral bud scales ± densely unicellular-hairy abaxially, margins usually unicellular-ciliate. Inflorescences 6-19-flowered; bracts similar to bud scales. Pedicels 4-17 mm, usually eglandular-hairy, rarely stipitate-glandular- and/or eglandular-hairy, otherwise sparsely to densely unicellular-hairy. Flowers opening before or with leaves, erect to horizontal, fragrant (usually musky-scented); calyx lobes 0.5-4 mm, surfaces and margins scattered stipitate-glandular- and/or eglandular-hairy, otherwise usually densely unicellular-hairy; corolla deep pink to white with pink tube, without blotch on upper lobe, funnelform, 23-46 mm, scattered, multicellular stipitate-glandular-hairy (hairs not forming distinct lines), otherwise sparsely to densely unicellular-hairy on outer surface, petals connate, lobes 7-20 mm, tube ± gradually expanded into lobes, 13-27 mm (equaling or longer than lobes); stamens 5, much exserted, ± unequal, 31-64 mm. Capsules borne on erect pedicels, 12-33 × 3-6.5 mm, usually sparsely to moderately eglandular-hairy, otherwise ± 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. Moist to dry woods, pocosins, swamps and savannas, often along streams; 0-500 m; Ala., Ark., Fla., Ga., Ill., Ky., La., Miss., N.C., Okla., S.C., Tenn., Tex.
Rhododendron canescens is most similar to R. prinophyllum and R. periclymenoides, although these three species do not constitute a clade (K. A. Kron 1993); they occasionally hybridize where their habitats and ranges overlap. In addition, putative hybrids with R. alabamense, R. atlanticum, R. austrinum, R. flammeum, R. periclymenoides, and R. calendulaceum are known.