Rhododendron albiflorum
Rhododendron cumberlandense
Cascade azalea, white rhododendron, white-flower azalea, white-flower rhododendron
Cumberland rhododendron, diploid flame or Cumberland azalea
bark ± smooth to furrowed;
twigs multicellular eglandular-hairy (hairs unbranched) and unicellular-hairy.
bark smooth to vertically furrowed, shredding;
twigs very sparsely to conspicuously multicellular eglandular-hairy (hairs unbranched), otherwise glabrous or densely unicellular-hairy.
deciduous;
petiole multicellular eglandular- and stipitate-glandular-hairy and unicellular-hairy;
blade narrowly elliptic or ovate to obovate, 2–9 × 0.8–3 cm, thin, membranous to chartaceous, margins minutely serrate, plane, ciliate when young, eglandular- and stipitate-glandular-hairy, apex acute to ± rounded, surfaces scattered eglandular-hairy, ± glabrescent.
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.
lateral (axillary, i.e., above leaf scars, spaced along shoots of previous year), fasciculate, 1–2-flowered;
bracts similar to bud scales.
3–7-flowered;
bracts similar to bud scales.
to 9–15 mm, eglandular- and stipitate-glandular-hairy.
4–9 mm, eglandular-hairy, rarely stipitate-glandular-hairy (then sepals eglandular), otherwise sparsely to densely unicellular-hairy.
± radially symmetric, opening soon after (and borne below) expanded leaves, pendulous, very fragrant (similar to vanilla and jasmine);
calyx lobes 5–17 mm, eglandular- and stipitate-glandular-hairy, margins glandular-hairy;
corolla white, rarely marked with yellow, bowl-shaped, 9–22 mm, minutely unicellular-hairy or glabrous on outer surface, petals connate, lobes 6–15 mm, tube expanding into lobes, 3–9 mm;
stamens 9(–12), included, ± unequal, 5.5–14 mm.
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, 6–8 × 5–6 mm, stipitate-glandular-, eglandular-, and unicellular-hairy.
borne on erect pedicels, 12–28 × 5–8 mm, sparsely to densely long stipitate-eglandular-hairy and sparsely to moderately unicellular-hairy.
with distinct tails;
testa closely appressed.
without distinct tails, flattened portion of testa may be well developed at each end;
testa expanded, dorsiventrally flattened, ± loose.
bud scales stipitate-glandular- and eglandular-hairy abaxially, margins stipitate-glandular-hairy.
bud scales glabrous abaxially, margins usually ciliate distally, glandular proximally.
= 26.
= 26.
Rhododendron albiflorum
Rhododendron cumberlandense
Rhododendron albiflorum is especially distinctive due to its axillary, white, somewhat pendulous, and nearly actinomorphic flowers, and it is placed in the monotypic subg. Candidastrum (Sleumer) Philipson & Philipson (W. R. Philipson and M. N. Philipson 1986). It is occasionally used as an ornamental. The disjunct population in Colorado has somewhat smaller calyx lobes and corollas and shorter stamens; it is sometimes recognized as var. warrenii (M. A. Lane et al. 1993). This variety is not recognized here because of the extent of morphological overlap between that population and those of the Pacific Northwest.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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.)
BC
OR
WA
Flora NW
PNW Herbaria
WildflowerSearch
iNaturalist
USDA Plants Database
