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clammy azalea, swamp azalea

early azalea, election-pink, hoary azalea, roseshell azalea

Habit Shrubs or trees, to 7 m, rhizomatous or not. Shrubs, to 3(–5) m, usually not rhizomatous.
Stems

bark smooth to vertically furrowed, shredding;

twigs 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.

Leaves

deciduous;

petiole usually multicellular eglandular-hairy and unicellular-hairy;

blade ovate to obovate, 2–7(–9) × 1–3(–3.8) cm, ± thin, membranous to chartaceous, margins entire or, sometimes, minutely serrulate, plane, ciliate, eglandular-hairy, apex acute to obtuse, often mucronate, abaxial surface glabrous or densely unicellular-hairy, adaxial surface (lustrous or dull), glabrous or sparsely scattered eglandular-hairy, sometimes also sparsely unicellular-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.

Inflorescences

3–14-flowered;

bracts similar to bud scales.

4–13-flowered;

bracts similar to bud scales.

Pedicels

5–27 mm, stipitate-glandular- or, sometimes, eglandular-hairy, otherwise sparsely to densely unicellular-hairy.

5–26 mm, usually stipitate-glandular-hairy, or, sometimes, also eglandular-hairy, otherwise sparsely to moderately unicellular-hairy.

Flowers

opening after leaves, erect to horizontal, slightly to strongly fragrant (most noticeable at night);

calyx lobes 0.5–5 mm, surfaces and margins scattered stipitate-glandular-hairy or, sometimes, eglandular-hairy, often also unicellular-hairy;

corolla white, sometimes pink-tinged or pink (not strongly contrasting with white or greenish to pinkish style or filaments), without blotch on upper lobe, funnelform, 20–58 mm, usually scattered, often conspicuously stipitate-glandular-hairy (hairs continuing in lines up lobes), otherwise sparsely to moderately unicellular-hairy on outer surface, petals connate, lobes 7–21 mm, tube usually ± gradually expanded into lobes, 13–37 mm (equaling or much longer than lobes);

stamens 5, much exserted, ± unequal, 21–65 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.

Capsules

borne on erect pedicels, 7–20 × 3–7 mm, usually densely stipitate-glandular- and/or eglandular-hairy, otherwise densely unicellular-hairy to ± glabrous.

borne on erect pedicel, 10–28 × 3–7 mm, stipitate-glandular-hairy, otherwise sparsely unicellular-hairy.

Seeds

without distinct tails, flattened portion of testa 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.

Floral

bud scales glabrous or densely unicellular-hairy abaxially (sometimes with sharply marked, dark brown band along distal margins), margins unicellular-ciliate or, sometimes, glandular-serrulate.

bud scales very sparsely to densely unicellular-hairy abaxially, especially near midvein, margins unicellular-ciliate.

2n

= 26.

= 26.

Rhododendron viscosum

Rhododendron prinophyllum

Phenology Flowering spring–summer. Flowering spring.
Habitat Acid swamps, bogs, seepage slopes, pocosins, streamheads and baygalls, wet pine flatwoods, moist pine or pine/oak forests, hummocks, shrub balds Acidic thickets or bogs, swampy to dry, rocky woods, bluffs, ravines, or along streams
Elevation 0-1500 m (0-4900 ft) 100-1500 m (300-4900 ft)
Distribution
from FNA
AL; AR; CT; DE; FL; GA; LA; MA; MD; ME; MS; NC; NH; NJ; NY; OK; PA; RI; SC; TN; TX; VA; VT
[WildflowerSearch map]
[BONAP county map]
from FNA
AL; AR; CT; IL; KY; MA; MD; MO; NC; NH; NJ; NY; OH; OK; PA; RI; TN; TX; VA; VT; WV
[WildflowerSearch map]
[BONAP county map]
Discussion

Rhododendron viscosum is the most widespread and variable species of sect. Pentanthera and has been divided into as many as four species: R. coryi, R. oblongifolium, R. serrulatum, and R. viscosum in the narrow sense. In addition, minor varieties and forms have been described. Because correlated or geographically coherent sets of character states cannot be discerned within this species, infraspecific taxa are not recognized here (K. A. Kron 1993). Rhododendron viscosum is most closely related to R. arborescens, and possibly also R. atlanticum. Hybrids with R. cumberlandense and R. arborescens are known. Plants with white corollas and a yellow blotch may be the result of hybridization.

(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.)

Source FNA vol. 8, p. 471. FNA vol. 8, p. 469.
Parent taxa Ericaceae > subfam. Ericoideae > Rhododendron Ericaceae > subfam. Ericoideae > Rhododendron
Sibling taxa
R. alabamense, R. albiflorum, R. arborescens, R. atlanticum, R. austrinum, R. calendulaceum, R. canadense, R. canescens, R. catawbiense, R. columbianum, R. cumberlandense, R. eastmanii, R. flammeum, R. groenlandicum, R. lapponicum, R. macrophyllum, R. maximum, R. minus, R. occidentale, R. periclymenoides, R. prinophyllum, R. prunifolium, R. tomentosum, R. vaseyi
R. alabamense, R. albiflorum, R. arborescens, R. atlanticum, R. austrinum, R. calendulaceum, R. canadense, R. canescens, R. catawbiense, R. columbianum, R. cumberlandense, R. eastmanii, R. flammeum, R. groenlandicum, R. lapponicum, R. macrophyllum, R. maximum, R. minus, R. occidentale, R. periclymenoides, R. prunifolium, R. tomentosum, R. vaseyi, R. viscosum
Synonyms Azalea viscosa, Azalea oblongifolia, Azalea serrulata, R. coryi, R. oblongifolium, R. serrulatum, R. viscosum var. serrulatum Azalea prinophylla
Name authority (Linnaeus) Torrey: Fl. N. Middle United States, 424. 1824 , (Small) Millais: Rhododendrons, 229. 1917 ,
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