Rhododendron calendulaceum
Rhododendron eastmanii
flame azalea
May white azalea, santee azalea
bark smooth to vertically furrowed, shredding;
twigs sparsely to conspicuously multicellular eglandular-hairy (hairs unbranched), otherwise sparsely to moderately unicellular-hairy.
bark smooth to vertically furrowed, shredding;
twigs unicellular and multicellular eglandular-hairy and unicellular-hairy.
deciduous;
petiole multicellular eglandular-hairy and unicellular-hairy;
blade ovate to obovate, 4.5–9.1 × 1.3–3.3 cm, thin, membranous to chartaceous, margins entire, plane, ciliate, eglandular-hairy, apex acute to obtuse, often mucronate, abaxial surface glabrous or densely eglandular-hairy, often also very sparsely to moderately unicellular-hairy, adaxial surface glabrous or sparsely scattered eglandular-hairy, often also sparsely unicellular-hairy.
deciduous;
petiole densely unicellular-hairy and sparsely to densely multicellular eglandular-hairy;
blade ovate or obovate to elliptic, 4.3–7.1 × 1.8–2.9 cm, membranous, margins entire, plane, ciliate, multicellular eglandular-hairy, apex acute to obtuse, mucronate, surfaces sparsely scattered, multicellular eglandular-hairy, abaxial surface moderately to densely unicellular-hairy and multicellular eglandular-hairy, midvein densely unicellular-hairy and multicellular eglandular-hairy, secondary veins sometimes multicellular eglandular-hairy, adaxial surface sparsely to densely unicellular-hairy, midvein densely unicellular-hairy.
5–9-flowered;
bracts similar to bud scales.
5–9 flowered;
bracts similar to bud scales.
7–14 mm, stipitate-glandular-hairy and/or eglandular-hairy, otherwise sparsely to densely unicellular-hairy.
5–11 mm, densely unicellular-hairy and sparsely to densely multicellular eglandular-hairy, sometimes multicellular glandular-hairy.
opening before or as leaves expand, erect to horizontal, acrid-scented;
calyx lobes 1–3 mm, scattered usually stipitate-glandular-hairy and unicellular-hairy, margins long stipitate-glandular-hairy and/or eglandular-hairy;
corolla orange to red-orange, with contrasting, darker-colored, orange to yellow blotch on upper lobe, funnelform, 30–54 mm, densely multicellular stipitate-glandular-hairy, otherwise sparsely to densely unicellular-hairy on outer surface, petals connate, lobes 14–30 mm, (spreading nearly as broadly as tube is long), tube abruptly expanding into lobes, 16–28 mm (longer than lobes);
stamens 5, much exserted, ± unequal, 52–72 mm.
opening after leaves have expanded, erect to horizontal, strongly fragrant (fresh during mid day);
calyx lobes 0.5–1 mm (often varying in length on same flower), margins setose, multicellular eglandular-hairy, abaxial surface sparsely to densely unicellular-hairy and multicellular eglandular-hairy, sometimes sparsely multicellular, weakly glandular-hairy;
corolla white, lobes pink tinged on newly opened flowers, with yellow to orange blotch on upper lobe (style white), funnelform, 24–50 mm, outer surface densely unicellular-hairy and sparsely to densely multicellular stipitate-glandular-hairy (glands usually weakly developed), inner surface densely unicellular-hairy, petals connate, upper lobe 9–17 mm, lateral lobes 11–25 mm, tube gradually expanding into lobes, 13–25 mm (equaling or much longer than lobes);
stamens 5, exserted, ± unequal, 45–67 mm.
borne on erect pedicels, 15–29 × 5–9 mm, sparsely to moderately long stipitate-glandular-hairy and/or eglandular-hairy, and sparsely unicellular-hairy.
borne on erect pedicels, 12–19 × 4–8 mm, sparsely to densely unicellular-hairy and multicellular eglandular-hairy.
without distinct tails, flattened portion of testa well developed at each end;
testa expanded, dorsiventrally flattened, ± loose.
without distinct tails, flattened portion of testa well developed at each end;
testa expanded, dorsiventrally flattened, ± loose.
bud scales usually glabrous abaxially, margins glandular.
bud scales glabrous abaxially, margins unicellular-ciliate near apex, glandular along proximal 2/3.
= 52.
Rhododendron calendulaceum
Rhododendron eastmanii
Rhododendron calendulaceum, frequently confused with the diploid R. cumberlandense, is an allotetraploid, and may have been derived from a hybrid between an ancestor of R. cumberlandense and one of R. prinophyllum (K. A. Kron 1993). It is distinguished from R. cumberlandense by its flowers opening before or with (versus after) the expansion of the leaves, glandular or eglandular (versus usually eglandular) pedicels, glandular or eglandular (versus usually eglandular) sepal margins (R. cumberlandense never with both pedicels and sepal margins glandular), and nonglaucous (versus often glaucous) abaxial leaf surface. Rhododendron calendulaceum is one of the showiest shrubs of the southern Appalachians; it is known to hybridize with R. prinophyllum and R. canescens.
Rhododendron calendulaceum and the remaining species (through 25. R. eastmanii) are the North American representatives of sect. Pentanthera G. Don, a group characterized by corollas that are typically unicellular-hairy on the outside and with a narrow tube, flowers with five, declinate, and usually much-exserted stamens, and seeds with ± loose testae (K. A. Kron 1993; Kron and M. Creel 1999). All species are used as ornamentals because of their colorful flowers(F. C. Galle 1985).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Older collections of Rhododendron eastmanii were typically referred to R. alabamense, which flowers early in the spring before the leaves have expanded, and has inflorescence bud scales are unicellular-ciliate; in R. eastmanii the bud scale margins are glandular.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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