Rhododendron arborescens

(Pursh) Torrey

Fl. N. Middle United States, 425. 1824 ,.

Common names: Sweet or smooth azalea
Endemic
Basionyms: Azalea arborescens Pursh Fl. Amer. Sept. 1: 152. 1813
Treatment appears in FNA Volume 8. Treatment on page 470. Mentioned on page 457, 471, 472.

Shrubs or trees, to 6 m, usually not rhizomatous. Stems: bark smooth to vertically furrowed, shredding; twigs glabrous or, very rarely, sparsely, widely scattered, unicellular and multicellular eglandular-hairy. Leaves deciduous; petiole glabrous or multicellular eglandular-hairy; blade ovate to obovate, 3–8 (–10.5) × 1.3–3.5 cm, thin, chartaceous, margins entire, plane, ciliate, eglandular-hairy, apex acute to obtuse, often mucronate, abaxial surface glabrous, (sometimes glaucous), adaxial surface glabrous, (lustrous). Floral bud-scales usually glabrous abaxially, margins unicellular-ciliate. Inflorescences 3–7-flowered; bracts similar to bud-scales. Pedicels 6–21 mm, glabrous or stipitate-glandular-hairy, sometimes also unicellular-hairy. Flowers opening after leaves, erect to horizontal, very fragrant; calyx lobes 0.8–6 (–9) mm, surfaces and margins scattered, stipitate-glandular and/or, sometimes, eglandular-hairy; corolla white or, sometimes, light pink (contrasting with dark-pink to red style and filaments), without blotch on upper lobe, funnelform, 30–55 mm, stipitate-glandular-hairy (hairs continuing in lines up lobes), otherwise glabrous or sparsely unicellular-hairy on outer surface, petals connate, lobes 10–24 mm, tube ± gradually expanded into lobes, 20–37 mm (equaling or much longer than lobes); stamens 5, much exserted, ± unequal, 44–82 mm. Capsules borne on erect pedicels, 8–17 × 4.5–8 mm, ± densely multicellular stipitate-glandular-hairy, sometimes also sparsely unicellular-hairy. Seeds without distinct tails; testa not dorsiventrally flattened, usually ± loose. 2n = 26.


Phenology: Flowering late spring–summer.
Habitat: Stream banks, rocky streamsides, heath balds, swampy woods or bogs
Elevation: 90-1500 m

Distribution

V8 920-distribution-map.gif

Ala., Ga., Ky., Md., N.C., Pa., S.C., Tenn., Va., W.Va.

Discussion

Rhododendron arborescens is most closely related to R. viscosum, as evidenced by their glabrous floral bud scales and flowers that appear after the leaves have expanded (K. A. Kron 1993). It can be distinguished by its glabrous branchlets, red style and filaments (which contrast with the white corollas), and distinctive seeds that lack loose, expanded testae. These two species occasionally hybridize; hybrids with R. cumberlandense also are known.

Selected References

None.

Lower Taxa

None.

... more about "Rhododendron arborescens"
Mucronate (?) +, Acute (?) +  and Obtuse (?) +
Walter S. Judd +  and Kathleen A. Kron +
(Pursh) Torrey +
smooth +  and vertically furrowed +
not flaky +
Azalea arborescens +
8 cm80 mm <br />0.08 m <br /> (10.5 cm105 mm <br />0.105 m <br />) +
3 cm30 mm <br />0.03 m <br /> (8 cm80 mm <br />0.08 m <br />) +
ovate;obovate +
coriaceous;membranous +
thin;1.3cm;3.5cm +
scale-like +
0.6 cm6 mm <br />0.006 m <br /> (0.9 cm9 mm <br />0.009 m <br />) +
0.08 cm0.8 mm <br />8.0e-4 m <br /> (0.6 cm6 mm <br />0.006 m <br />) +
multicellular +
0.8 cm8 mm <br />0.008 m <br /> (1.7 cm17 mm <br />0.017 m <br />) +
unicellular-hairy +  and stipitate-glandular-hairy +
0.45 cm4.5 mm <br />0.0045 m <br /> (0.8 cm8 mm <br />0.008 m <br />) +
Sweet or smooth azalea +
light pink +, , +  and white +
unicellular-hairy +, glabrous +  and stipitate-glandular-hairy +
rotate to crateriform campanulate cylindric globose or urceolate +
3 cm30 mm <br />0.03 m <br /> (5.5 cm55 mm <br />0.055 m <br />) +
Ala. +, Ga. +, Ky. +, Md. +, N.C. +, Pa. +, S.C. +, Tenn. +, Va. +  and W.Va. +
90-1500 m +
undifferentiated +
fusiform +
fragrant +
erect +  and horizontal +
usually ovoid;cylindric +
Stream banks, rocky streamsides, heath balds, swampy woods or bogs +
multicellular +
terminal +  and axillary +
deciduous +
10mm +  and 24mm +
unicellular-ciliate +  and ciliate +
eglandular-hairy +  and stipitate-glandular +
parietal +, axile +  and placentation +
tenuinucellate +  and unitegmic +
unicellular-hairy +, stipitate-glandular-hairy +  and glabrous +
0.6 cm6 mm <br />0.006 m <br /> (2.1 cm21 mm <br />0.021 m <br />) +
scale-like +
reduced +
not sticky +
eglandular-hairy +, multicellular +  and glabrous +
Flowering late spring–summer. +
4-5-carpellate +
Fl. N. Middle United States, +
distinct +
tailed +, flattened-ellipsoidal +  and fusiform +
unequal +
procumbent +  and prostrate +
creeping +  and sprawling +
peltate +  and capitate +
straight +
eglandular-hairy +  and stipitate-glandular +
Undefined tribe Empetraceae +
distinct +
Rhododendron arborescens +
Rhododendron +
species +
flattened +
expanded +
2 cm20 mm <br />0.02 m <br /> (3.7 cm37 mm <br />0.037 m <br />) +
multicellular +  and unicellular +
eglandular-hairy +, , +  and glabrous +
evergreen +, deciduous +  and perennial +
tree +  and shrub +
heterotrophic +, autotrophic +  and mycotrophic +