Rhododendron occidentale |
Rhododendron viscosum |
|
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California azalea, western azalea |
clammy azalea, swamp azalea |
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Habit | Shrubs or trees, to 8(–10) m, usually not rhizomatous. | Shrubs or trees, to 7 m, rhizomatous or not. |
Stems | bark smooth to vertically furrowed, shredding; twigs sparsely to densely multicellular stipitate-glandular-hairy or unicellular-hairy, or glabrous, sometimes only unicellular-hairy. |
bark smooth to vertically furrowed, shredding; twigs sparsely to conspicuously multicellular eglandular-hairy (hairs unbranched), otherwise glabrous or densely unicellular-hairy. |
Leaves | deciduous; petiole multicellular eglandular- or stipitate-glandular-hairy and unicellular-hairy; blade ovate or obovate to elliptic, (2.5–)3.5–8.2(–10.8) × 1.2–2.9(–3.6) cm, thin, membranous, margins entire, plane, ciliate, eglandular-hairy, sometimes also stipitate-glandular-hairy, apex acute to obtuse, often mucronate, abaxial surface glabrous or sparsely unicellular-hairy, often also stipitate-glandular-hairy (or, rarely, stipitate-glandular- and eglandular-hairy), adaxial surface sparsely scattered, multicellular eglandular- and/or stipitate-glandular-hairy and unicellular-hairy, or glabrous. |
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. |
Inflorescences | 3–15-flowered; bracts similar to bud scales. |
3–14-flowered; bracts similar to bud scales. |
Pedicels | 9–26 mm, stipitate-glandular- and, sometimes, also eglandular-hairy. |
5–27 mm, stipitate-glandular- or, sometimes, eglandular-hairy, otherwise sparsely to densely unicellular-hairy. |
Flowers | opening with leaves or after they have expanded, erect to horizontal, fragrant or mephitic-scented; calyx lobes 1–4(–9) mm, often stipitate-glandular- and/or eglandular-hairy, sometimes also unicellular-hairy, margins usually stipitate-glandular-hairy; corolla white with contrasting yellow blotch on upper lobe, white and pink or salmon, or pink with orange blotch on upper lobe, rarely white with yellow lines at throat, or with tube white to red, funnelform, 30–58 mm, stipitate-glandular-hairy and, rarely, also eglandular-hairy, otherwise sparsely to moderately unicellular-hairy or these hairs absent on outer surface, petals connate, lobes 13–29 mm, tube gradually expanding into lobes, 15–29 mm (equaling or longer than lobes); stamens 5, much exserted, ± unequal, 40–75 mm. |
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. |
Capsules | borne on erect pedicels, 12–22 × 4–14 mm, multicellular stipitate-glandular-hairy, sometimes also eglandular-hairy, otherwise sparsely unicellular-hairy (unicellular hairs rarely absent). |
borne on erect pedicels, 7–20 × 3–7 mm, usually densely stipitate-glandular- and/or eglandular-hairy, otherwise densely unicellular-hairy to ± glabrous. |
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 sparsely to densely unicellular-hairy abaxially, rarely also sparsely eglandular- or stipitate-glandular-hairy, margins unicellular-ciliate, or with glands and cilia mixed, or glandular. |
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. |
2n | = 26. |
= 26. |
Rhododendron occidentale |
Rhododendron viscosum |
|
Phenology | Flowering spring–summer. | Flowering spring–summer. |
Habitat | Moist, wooded slopes and canyon bottoms, along streams, thickets, bogs, serpentine ridges, ocean bluffs | Acid swamps, bogs, seepage slopes, pocosins, streamheads and baygalls, wet pine flatwoods, moist pine or pine/oak forests, hummocks, shrub balds |
Elevation | 0-2700 m (0-8900 ft) | 0-1500 m (0-4900 ft) |
Distribution |
CA; OR
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AL; AR; CT; DE; FL; GA; LA; MA; MD; ME; MS; NC; NH; NJ; NY; OK; PA; RI; SC; TN; TX; VA; VT
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Discussion | The flowers of Rhododendron occidentale show an exceptional range of variation in color. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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.) |
Source | FNA vol. 8, p. 467. | FNA vol. 8, p. 471. |
Parent taxa | Ericaceae > subfam. Ericoideae > Rhododendron | Ericaceae > subfam. Ericoideae > Rhododendron |
Sibling taxa | ||
Synonyms | Azalea occidentalis, Azalea californica, R. occidentale var. paludosum, R. sonomense | Azalea viscosa, Azalea oblongifolia, Azalea serrulata, R. coryi, R. oblongifolium, R. serrulatum, R. viscosum var. serrulatum |
Name authority | (Torrey & A. Gray) A. Gray: in W. H. Brewer et al., Bot. California 1: 458. 1876 , | (Linnaeus) Torrey: Fl. N. Middle United States, 424. 1824 , |
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