Rhododendron tomentosum |
Rhododendron occidentale |
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Labrador tea, marsh Labrador tea, northern Labrador tea, trappers tea |
California azalea, western azalea |
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Habit | Shrubs, to 0.5 m, rhizomatous. | Shrubs or trees, to 8(–10) m, usually not rhizomatous. |
Stems | creeping or prostrate; bark ± smooth; twigs unicellular-hairy and with flattened, glandular scales, scales often obscured by dense, ferruginous, long-crisped, multicellular hairs. |
bark smooth to vertically furrowed, shredding; twigs sparsely to densely multicellular stipitate-glandular-hairy or unicellular-hairy, or glabrous, sometimes only unicellular-hairy. |
Leaves | persistent, (fragrant when crushed); petiole with unicellular and/or peltate scales and, sometimes, ferruginous, long-crisped hairs; blade ± linear, 2–5 × 1–4 cm (often much longer than wide), coriaceous, margins entire, revolute, glabrous, apex acute, abaxial surface with sparse to dense, glandular-peltate scales without broad rim, scales often obscured by dense (to sparse), ferruginous, long-crisped, multicellular hairs sometimes forming dense, ± uniform mat, adaxial surface rugose with scattered, lepidote scales and sometimes also with white, unicellular hairs along impressed midrib, midrib usually lanate. |
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. |
Inflorescences | slightly rounded, 10–35-flowered; bracts lepidote abaxially, margins ciliate, long-crisped-hairy, sometimes also unicellular-hairy. |
3–15-flowered; bracts similar to bud scales. |
Pedicels | 5–26 mm, sparsely eglandular-hairy (hairs ferruginous, elongated), with ferruginous, long-crisped, unicellular and/or peltate scales, sometimes also long-stalked, multicellular glandular-hairy. |
9–26 mm, stipitate-glandular- and, sometimes, also eglandular-hairy. |
Flowers | radially symmetric, opening after leaves (of flowering shoots), ± erect, not fragrant; calyx lobes ca. 1 mm, outer surface densely to sparsely unicellular-hairy (hairs tan), and multicellular, stipitate-glandular-hairy (hairs red) on margins; corolla white to cream, without blotch, ± rotate, 2–8 mm, inner surface often densely unicellular-hairy, petals appearing distinct or only slightly connate basally, lobes 5–7 mm; stamens 10, exserted, ± equal, 4.4–8.5 mm. |
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. |
Capsules | borne on apex of sharply recurved pedicels, 2.5–5 × 1–3 mm (only slightly longer than wide), with sparse to dense, lepidote scales, acropetally dehiscent. |
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). |
Seeds | somewhat elongated beyond narrow ends; testa closely appressed. |
without distinct tails, flattened portion of testa well developed at each end; testa expanded, dorsiventrally flattened, ± loose. |
Floral | bud scales with lepidote scales and unicellular-hairy abaxially, margins unicellular-hairy. |
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. |
2n | = 26, 52. |
= 26. |
Rhododendron tomentosum |
Rhododendron occidentale |
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Phenology | Flowering spring–summer. | Flowering spring–summer. |
Habitat | Bogs, muskeg, tundra, raised beach ridges | Moist, wooded slopes and canyon bottoms, along streams, thickets, bogs, serpentine ridges, ocean bluffs |
Elevation | 0-1800 m (0-5900 ft) | 0-2700 m (0-8900 ft) |
Distribution |
AK; AB; BC; MB; NF; NT; NU; ON; QC; SK; YT; Greenland; Europe; Asia
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CA; OR
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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.) |
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Source | FNA vol. 8, p. 459. | FNA vol. 8, p. 467. |
Parent taxa | Ericaceae > subfam. Ericoideae > Rhododendron | Ericaceae > subfam. Ericoideae > Rhododendron |
Sibling taxa | ||
Synonyms | Ledum palustre, Ledum decumbens, Ledum palustre subsp. decumbens, R. subarcticum, R. tolmachevii, R. tomentosum subsp. decumbens, R. tomentosum var. subarcticum | Azalea occidentalis, Azalea californica, R. occidentale var. paludosum, R. sonomense |
Name authority | Harmaja: Ann. Bot. Fenn. 27: 204. (1990) | (Torrey & A. Gray) A. Gray: in W. H. Brewer et al., Bot. California 1: 458. 1876 , |
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