Rhododendron macrophyllum |
Rhododendron flammeum |
|
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big leaf rhododendron, California rhododendron, California rose bay, coast rhododendron, Pacific rhododendron, western rhododendron |
oconee azalea, Piedmont azalea |
|
Habit | Shrubs or trees, to 5 m, sometimes rhizomatous. | Shrubs, to 2.5 m, usually not rhizomatous. |
Stems | bark smooth to vertically furrowed, shredding; twigs with basally branched, crisped/matted, eglandular hairs, very quickly glabrate. |
bark smooth to vertically furrowed, shredding; twigs conspicuously multicellular eglandular-hairy (hairs unbranched), otherwise sparsely to densely unicellular-hairy. |
Leaves | persistent; petiole glabrous; blade elliptic to slightly ovate or obovate, (6–)8.5–14(–20) × 2.5–5.5(–7.5) cm, thick, coriaceous, margins entire, plane to revolute, glabrous, apex acute to obtuse or slightly acuminate, surfaces scattered eglandular-hairy (hairs branched basally, crisped, very quickly deciduous), abaxial surface ± smooth. |
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 | 10–20-flowered; bracts similar to bud scales. |
6–11-flowered; bracts similar to bud scales. |
Pedicels | 30–60 mm, glabrous. |
3–12 mm, eglandular-hairy, otherwise moderately unicellular-hairy to glabrate. |
Flowers | opening after development of leaves (of flowering shoots), erect to horizontal, fragrant; calyx lobes 1–1.5 mm, glabrous, except margins eglandular- and stipitate-glandular-hairy; corolla white to pink or rose-purple, with yellowish green spots on upper lobe, broadly campanulate, 24–48 mm, outer surface glabrous, petals connate, lobes 14–30 mm, tube gradually expanding into lobes, 10–23 mm; stamens 10, included, ± unequal, 16–37 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 erect pedicels, 13–25 × 4–7 mm, eglandular-hairy (hairs ferruginous, branched or unbranched) and, often, stipitate-glandular-hairy. |
borne on erect pedicels, 15–30 × 4.5–8 mm, densely, stiffly eglandular-hairy and 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 devloped at each end; testa expanded, dorsiventrally flattened, ± loose. |
Floral | bud scales multicellular eglandular-hairy (hairs branched basally), and unicellular-hairy (hairs short to elongate) abaxially, margins eglandular-hairy (hairs branched). |
bud scales glabrous or densely unicellular-hairy abaxially, margins densely unicellular-ciliate. |
2n | = 26. |
= 26. |
Rhododendron macrophyllum |
Rhododendron flammeum |
|
Phenology | Flowering spring–summer. | Flowering spring. |
Habitat | Forest and forest margins, thickets | Open dry woods, slopes and ridges, stream bluffs |
Elevation | 50-1600 m (200-5200 ft) | 20-500 m (100-1600 ft) |
Distribution |
CA; OR; WA; BC
|
GA; SC |
Discussion | Rhododendron macrophyllum, R. maximum, and R. catawbiense represent subg. Hymenanthes (Blume) K. Koch in North America; the subgenus is represented by hundreds of species in temperate eastern Asia and is characterized by its branched, eglandular hairs (D. F. Chamberlain 1982). These showy plants are frequently used as ornamentals. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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.) |
Source | FNA vol. 8, p. 462. | FNA vol. 8, p. 466. |
Parent taxa | Ericaceae > subfam. Ericoideae > Rhododendron | Ericaceae > subfam. Ericoideae > Rhododendron |
Sibling taxa | ||
Synonyms | R. californicum | Azalea calendulacea var. flammea |
Name authority | D. Don ex G. Don: Gen. Hist. 3: 843. 1834 , | (Michaux) Sargent: Rhododendron Soc. Notes 1: 120. 1917 , |
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