Rhododendron cumberlandense
Rhododendron prinophyllum
Cumberland rhododendron, diploid flame or Cumberland azalea
early azalea, election-pink, hoary azalea, roseshell azalea
bark smooth to vertically furrowed, shredding;
twigs very sparsely to conspicuously multicellular eglandular-hairy (hairs unbranched), otherwise glabrous or densely unicellular-hairy.
bark smooth to vertically furrowed, shredding;
twigs scattered, multicellular eglandular-hairy (hairs unbranched), otherwise densely to sparsely 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.
deciduous;
petiole usually multicellular eglandular-hairy and unicellular-hairy;
blade ovate to obovate, 3–9 × 1.2–3.7 cm, thin, membranous, margins entire, plane, conspicuously ciliate, eglandular-hairy (hairs ascending away from margins), apex acute to obtuse, often mucronate, abaxial surface sparsely to densely unicellular-hairy, sometimes also eglandular-hairy, adaxial surface usually sparsely unicellular-hairy, sometimes glabrous, often also scattered eglandular-hairy.
3–7-flowered;
bracts similar to bud scales.
4–13-flowered;
bracts similar to bud scales.
4–9 mm, eglandular-hairy, rarely stipitate-glandular-hairy (then sepals eglandular), otherwise sparsely to densely unicellular-hairy.
5–26 mm, usually stipitate-glandular-hairy, or, sometimes, also eglandular-hairy, otherwise sparsely to moderately 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.
opening before or with leaves, erect to horizontal, fragrant (spicy-scented);
calyx lobes 0.5–4 mm, surfaces and margins scattered stipitate-glandular- and/or eglandular-hairy, otherwise sparsely to densely unicellular-hairy;
corolla usually bright pink, without blotch on upper lobe, funnelform, 25–45 mm, scattered, multicellular stipitate-glandular-hairy (hairs not forming distinct lines), otherwise sparsely to moderately unicellular-hairy on outer surface, petals connate, lobes 10–23 mm, tube gradually expanded into lobes, 11–27 mm (equaling or longer than lobes);
stamens 5, much exserted, ± unequal, 32–53 mm.
borne on erect pedicels, 12–28 × 5–8 mm, sparsely to densely long stipitate-eglandular-hairy and sparsely to moderately unicellular-hairy.
borne on erect pedicel, 10–28 × 3–7 mm, stipitate-glandular-hairy, otherwise sparsely unicellular-hairy.
without distinct tails, flattened portion of testa may be 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 glabrous abaxially, margins usually ciliate distally, glandular proximally.
bud scales very sparsely to densely unicellular-hairy abaxially, especially near midvein, margins unicellular-ciliate.
= 26.
= 26.
Rhododendron cumberlandense
Rhododendron prinophyllum
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.)
Rhododendron prinophyllum is unusual in its strongly disjunct distribution. Plants in the western portion of the range often have longer corolla tubes and are most similar to R. canescens and R. periclymenoides, and can be distinguished from both by their broader, more gradually expanded corolla tubes and usually consistently glandular sepal margins, pedicels, and ovaries. Hybrids are known with R. calendulaceum and R. periclymenoides. The name R. roseum (Loiseleur) Rehder, which has been used for this species, is illegitimate because it was superfluous when published (K. A. Kron 1989).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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