Rhododendron cumberlandense
Cumberland rhododendron, diploid flame or Cumberland azalea
bark smooth to vertically furrowed, shredding;
twigs very sparsely to conspicuously multicellular eglandular-hairy (hairs unbranched), otherwise glabrous or densely unicellular-hairy.
deciduous;
petiole usually multicellular eglandular-hairy and usually unicellular-hairy;
blade ovate to obovate, 3.1–8.1 × 1.3–3.5 cm, thin, membranous to chartaceous, margins entire, plane, unicellular-ciliate, apex acute to obtuse, often mucronate, abaxial surface glabrous or very sparsely eglandular-hairy, (usually glaucous), adaxial surface glabrous or sparsely scattered eglandular-hairy.
3–7-flowered;
bracts similar to bud scales.
4–9 mm, eglandular-hairy, rarely stipitate-glandular-hairy (then sepals eglandular), otherwise sparsely to densely unicellular-hairy.
opening after leaves have expanded, erect to horizontal, acrid-scented;
calyx lobes 1–3 mm, scattered, long-stipitate, usually eglandular-hairy, and unicellular-hairy, margins extremely long stipitate-eglandular-hairy (rarely long stipitate-glandular-hairy, then pedicels eglandular);
corolla red, with indistinct blotch or darker-colored region on upper lobe, funnelform, 27–45 mm, scattered stipitate-glandular-hairy, otherwise ± densely unicellular-hairy on outer surface, petals connate, lobes 14–30 mm, tube abruptly expanding into lobes, 14–24 mm (equaling or much longer than lobes);
stamens 5, much exserted, ± unequal, 42–62 mm.
borne on erect pedicels, 12–28 × 5–8 mm, sparsely to densely long stipitate-eglandular-hairy and sparsely to moderately unicellular-hairy.
without distinct tails, flattened portion of testa may be well developed at each end;
testa expanded, dorsiventrally flattened, ± loose.
bud scales glabrous abaxially, margins usually ciliate distally, glandular proximally.
= 26.
Rhododendron cumberlandense
Rhododendron cumberlandense has a geographic distribution that is concentrated in the Cumberland Plateau and Mountains region with some populations in the southern Blue Ridge. It is most closely related to R. calendulaceum and can be distinguished from the latter by its flowering well after the leaves have expanded, eglandular pedicel and sepal margins, and usually abaxially conspicuously glaucous leaves. Hybrids are known with R. arborescens and R. viscosum. Rhododendron bakeri (Lemmon) Skinner very likely represents a hybrid between R. flammeum and R. canescens, although it has often been synonymized with R. cumberlandense (see K. A. Kron 1993).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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