Rhododendron tomentosum |
Rhododendron flammeum |
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Labrador tea, marsh Labrador tea, northern Labrador tea, trappers tea |
oconee azalea, Piedmont azalea |
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Habit | Shrubs, to 0.5 m, rhizomatous. | Shrubs, to 2.5 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 conspicuously multicellular eglandular-hairy (hairs unbranched), otherwise sparsely to densely 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-hairy and unicellular-hairy; blade ovate to obovate, 2.9–8.5 × 1.2–3.5 cm, thin, membranous to chartaceous, margins entire, plane, ciliate, eglandular-hairy, apex acute to obtuse, often mucronate, abaxial surface glabrous or densely unicellular-hairy and/or eglandular-hairy, adaxial surface scattered eglandular-hairy, otherwise sparsely unicellular-hairy, glabrate in age. |
Inflorescences | slightly rounded, 10–35-flowered; bracts lepidote abaxially, margins ciliate, long-crisped-hairy, sometimes also unicellular-hairy. |
6–11-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. |
3–12 mm, eglandular-hairy, otherwise moderately unicellular-hairy to glabrate. |
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 before or with development of leaves, erect to horizontal, acrid-scented; calyx lobes 0.5–5 mm, glabrous or unicellular-hairy and eglandular-hairy, margins eglandular-hairy; corolla bright red to orange-red or orange, with contrasting, darker-colored, orange or yellow-orange blotch on upper lobe, funnelform, 27–51 mm, scattered, multicellular eglandular-hairy (sometimes very weakly stipitate-glandular-hairy), otherwise sparsely to moderately unicellular-hairy on outer surface, petals connate, lobes 8–22 mm (spreading nearly as broadly as tube is long), tube rather abruptly to gradually expanded into lobes, 17–34 mm, longer than lobes; stamens 5, much exserted, ± unequal, 40–73 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, 15–30 × 4.5–8 mm, densely, stiffly eglandular-hairy and unicellular-hairy. |
Seeds | somewhat elongated beyond narrow ends; testa closely appressed. |
without distinct tails, flattened portion of testa well devloped at each end; testa expanded, dorsiventrally flattened, ± loose. |
Floral | bud scales with lepidote scales and unicellular-hairy abaxially, margins unicellular-hairy. |
bud scales glabrous or densely unicellular-hairy abaxially, margins densely unicellular-ciliate. |
2n | = 26, 52. |
= 26. |
Rhododendron tomentosum |
Rhododendron flammeum |
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Phenology | Flowering spring–summer. | Flowering spring. |
Habitat | Bogs, muskeg, tundra, raised beach ridges | Open dry woods, slopes and ridges, stream bluffs |
Elevation | 0-1800 m (0-5900 ft) | 20-500 m (100-1600 ft) |
Distribution |
AK; AB; BC; MB; NF; NT; NU; ON; QC; SK; YT; Greenland; Europe; Asia
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GA; SC |
Discussion | Rhododendron flammeum is closely related to R. calendulaceum, R. cumberlandense, and R. prunifolium, all of which are characterized by orange to red flowers that lack a sweet fragrance (K. A. Kron 1993). The growth form of R. flammeum is relatively flat-topped compared to the growth form of most of the other species of azaleas. Hybrids with R. canescens are known. The name R. speciosum (Willdenow) Sweet is often used for this species; that name is based on Azalea speciosa Willdenow, a superfluous name that refers to R. calendulaceum. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Source | FNA vol. 8, p. 459. | FNA vol. 8, p. 466. |
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 calendulacea var. flammea |
Name authority | Harmaja: Ann. Bot. Fenn. 27: 204. (1990) | (Michaux) Sargent: Rhododendron Soc. Notes 1: 120. 1917 , |
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