Rhododendron albiflorum
Rhododendron prunifolium
Cascade azalea, white rhododendron, white-flower azalea, white-flower rhododendron
plumleaf azalea
bark ± smooth to furrowed;
twigs multicellular eglandular-hairy (hairs unbranched) and unicellular-hairy.
bark smooth to vertically furrowed, shredding;
twigs glabrous.
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 unicellular-hairy;
blade ovate to obovate, 3–11(–15.2) × 1–4(–5) cm, thin, membranous to chartaceous, margins entire, plane, ciliate, eglandular-hairy, apex acute to obtuse, often mucronate, abaxial surface glabrous, adaxial surface glabrous or, rarely, 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.
4–7-flowered;
bracts similar to bud scales.
to 9–15 mm, eglandular- and stipitate-glandular-hairy.
5–12 mm, eglandular-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 development of leaves, erect to horizontal, not fragrant;
calyx lobes 1–3(–4) mm, glabrous or sparsely unicellular-hairy, margins eglandular-hairy;
corolla red to orange-red or orange, with indistinct darker blotch on upper lobe, funnelform, 36–53 mm, glabrous or very sparsely long stipitate-glandular-hairy, sometimes also sparsely unicellular-hairy on outer surface, petals connate, lobes 11–22 mm, tube abruptly expanded into lobes, 23–35 mm (± equaling or much longer than lobes);
stamens 5, much exserted, ± unequal, 64–84 mm.
borne on erect pedicels, 6–8 × 5–6 mm, stipitate-glandular-, eglandular-, and unicellular-hairy.
borne on erect pedicels, 15–22 × 4.5–7 mm, densely, stiffly eglandular-hairy and sparsely unicellular-hairy.
with distinct tails;
testa closely appressed.
without distinct tails, flattened portion of testa 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 unicellular-ciliate.
= 26.
= 26.
Rhododendron albiflorum
Rhododendron prunifolium
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.)
Of conservation concern.
Rhododendron prunifolium is most closely related to R. flammeum, R. cumberlandense, and R. calendulaceum, and can be distinguished from all of those orange- to red-flowered species by its nearly glabrous and more gradually expanded corolla tube and by the indistinct nature of the floral blotch (K. A. Kron 1993). This species is federally protected.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
BC
OR
WA
Flora NW
PNW Herbaria
WildflowerSearch
iNaturalist
USDA Plants Database
