Rhododendron albiflorum

Hooker

Fl. Bor.-Amer. 2: 43, plate 133. 1834 ,.

Common names: White rhododendron
Endemic
Synonyms: Azaleastrum albiflorum (Hooker) Rydberg Rhododendron albiflorum var. warrenii (A. Nelson) M. A. Lane
Treatment appears in FNA Volume 8. Treatment on page 464. Mentioned on page 455, 457.

Shrubs, to 2.5 m, rhizomatous. Stems: bark ± smooth to furrowed; twigs multicellular eglandular-hairy (hairs unbranched) and unicellular-hairy. Leaves 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. Floral bud-scales stipitate-glandular and eglandular-hairy abaxially, margins stipitate-glandular-hairy. Inflorescences lateral (axillary, i.e., above leaf-scars, spaced along shoots of previous year), fasciculate, 1–2-flowered; bracts similar to bud-scales. Pedicels to 9–15 mm, eglandular and stipitate-glandular-hairy. Flowers ± 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. Capsules borne on erect pedicels, 6–8 × 5–6 mm, stipitate-glandular, eglandular, and unicellular-hairy. Seeds with distinct tails; testa closely appressed. 2n = 26.


Phenology: Flowering late spring–summer.
Habitat: Coniferous forests, alpine thickets, stream banks, seeps on rock outcrops
Elevation: 800-3500 m

Distribution

V8 907-distribution-map.gif

Alta., B.C., Colo., Idaho, Mont., Oreg., Wash.

Discussion

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.

Selected References

None.

Lower Taxa

None.

... more about "Rhododendron albiflorum"
Walter S. Judd +  and Kathleen A. Kron +
Hooker +
less smooth +  and furrowed +
not flaky +
2 cm20 mm <br />0.02 m <br /> (9 cm90 mm <br />0.09 m <br />) +
ovate;obovate +
membranous;chartaceous +
thin;0.8cm;3cm +
scale-like +
stipitate-glandular-hairy +
0.5 cm5 mm <br />0.005 m <br /> (1.7 cm17 mm <br />0.017 m <br />) +
0.6 cm6 mm <br />0.006 m <br /> (0.8 cm8 mm <br />0.008 m <br />) +
unicellular-hairy +  and stipitate-glandular +
0.5 cm5 mm <br />0.005 m <br /> (0.6 cm6 mm <br />0.006 m <br />) +
White rhododendron +
glabrous +  and unicellular-hairy +
rotate to crateriform campanulate cylindric globose or urceolate +
0.9 cm9 mm <br />0.009 m <br /> (2.2 cm22 mm <br />0.022 m <br />) +
Alta. +, B.C. +, Colo. +, Idaho +, Mont. +, Oreg. +  and Wash. +
800-3500 m +
undifferentiated +
fusiform +
eglandular-hairy +  and stipitate-glandular +
fragrant +
usually ovoid;cylindric +
Coniferous forests, alpine thickets, stream banks, seeps on rock outcrops +
multicellular +
deciduous +
expanded +
6mm +  and 15mm +
glandular-hairy +  and stipitate-glandular-hairy +
parietal +, axile +  and placentation +
tenuinucellate +  and unitegmic +
stipitate-glandular-hairy +
0.9 cm9 mm <br />0.009 m <br /> (1.5 cm15 mm <br />0.015 m <br />) +
scale-like +
reduced +
not sticky +
eglandular +  and multicellular +
unicellular-hairy +  and stipitate-glandular-hairy +
Flowering late spring–summer. +
4-5-carpellate +
Fl. Bor.-Amer. +
distinct +
tailed +, flattened-ellipsoidal +  and fusiform +
unequal +
procumbent +  and prostrate +
creeping +  and sprawling +
peltate +  and capitate +
straight +
glabrescent +  and eglandular-hairy +
Azaleastrum albiflorum +  and Rhododendron albiflorum var. warrenii +
distinct +
Rhododendron albiflorum +
Rhododendron +
species +
expanding +
0.3 cm3 mm <br />0.003 m <br /> (0.9 cm9 mm <br />0.009 m <br />) +
multicellular +
unicellular-hairy +  and eglandular-hairy +
evergreen +, deciduous +  and perennial +
heterotrophic +, autotrophic +  and mycotrophic +