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Lapland rhododendron, Lapland rose-bay

plumleaf azalea

Habit Shrubs, to 0.5(–0.7) m, rhizomatous. Shrubs or trees, to 5(–6) m, usually not rhizomatous.
Stems

prostrate to erect;

bark ± smooth to vertically furrowed, shredding;

twigs with straw-colored to ferruginous, multicellular, broad-rimmed, peltate scales and unicellular-hairy.

bark smooth to vertically furrowed, shredding;

twigs glabrous.

Leaves

persistent;

petiole with broad-rimmed, glandular-peltate scales;

blade oblong-elliptic to elliptic, ovate, or obovate, 0.4–2(–2.5) × 0.2–0.7(–0.9) cm, coriaceous, margins entire, plane to revolute, with broad-rimmed scales, apex obtuse to rounded or mucronate, surfaces with conspicuous, straw-colored or golden to ferruginous, broad-rimmed, glandular-peltate scales and unicellular-hairy abaxially.

deciduous;

petiole usually multicellular eglandular-hairy and unicellular-hairy;

blade ovate to obovate, 3–11(–15.2) × 1–4(–5) cm, thin, membranous to chartaceous, margins entire, plane, ciliate, eglandular-hairy, apex acute to obtuse, often mucronate, abaxial surface glabrous, adaxial surface glabrous or, rarely, sparsely scattered eglandular-hairy.

Inflorescences

fasciculate racemes, 3–6-flowered;

bracts similar to bud scales.

4–7-flowered;

bracts similar to bud scales.

Pedicels

2.5–14 mm, with ferruginous scales and often unicellular-hairy.

5–12 mm, eglandular-hairy.

Flowers

opening before development of leaves, erect to horizontal, fragrant;

calyx lobes 0.5–2 mm, with ferruginous scales and unicellular-hairy, margins ciliate, unicellular and multicellular eglandular-hairy;

corolla rose to purple, sometimes white, without blotch, broadly funnelform, (6.5–)7.5–14(–15) mm, glabrous on outer surface, petals connate (for 3/4+ their lengths), lobes 4.5–8.5 mm, tube gradually expanding into lobes, 1.5–6.5 mm;

stamens 5–10, slightly exserted, ± unequal, 7–13 mm;

filaments glabrous or proximally unicellular-hairy.

opening after development of leaves, erect to horizontal, not fragrant;

calyx lobes 1–3(–4) mm, glabrous or sparsely unicellular-hairy, margins eglandular-hairy;

corolla red to orange-red or orange, with indistinct darker blotch on upper lobe, funnelform, 36–53 mm, glabrous or very sparsely long stipitate-glandular-hairy, sometimes also sparsely unicellular-hairy on outer surface, petals connate, lobes 11–22 mm, tube abruptly expanded into lobes, 23–35 mm (± equaling or much longer than lobes);

stamens 5, much exserted, ± unequal, 64–84 mm.

Capsules

borne on erect pedicels, 4–7 × 2–3 mm, with ferruginous, peltate scales and unicellular-hairy.

borne on erect pedicels, 15–22 × 4.5–7 mm, densely, stiffly eglandular-hairy and sparsely unicellular-hairy.

Seeds

without distinct tails;

testa closely appressed.

without distinct tails, flattened portion of testa well developed at each end;

testa expanded, dorsiventrally flattened, ± loose.

Floral

bud scales ferruginous-lepidote, sometimes also unicellular-hairy abaxially, margins ± ciliate, unicellular and multicellular, elongate eglandular-hairy.

bud scales glabrous abaxially, margins unicellular-ciliate.

2n

= 26, 52.

= 26.

Rhododendron lapponicum

Rhododendron prunifolium

Phenology Flowering spring–summer. Flowering summer.
Habitat Arctic and alpine tundra, rocky barrens and heaths or thickets, raised beach ridges, sandy stream banks Shady forests, especially ravines along streams
Elevation 0-1900 m (0-6200 ft) 30-200 m (100-700 ft)
Distribution
from FNA
AK; ME; NH; NY; WI; AB; BC; MB; NF; NS; NT; NU; ON; QC; YT; Greenland; Europe (Russia, Scandinavia); Asia (Siberia)
[WildflowerSearch map]
[BONAP county map]
from FNA
AL; GA
[WildflowerSearch map]
[BONAP county map]
Discussion

Rhododendron lapponicum is known to hybridize with R. tomentosum in Greenland, producing R. ×vanhoeffenii Abromeit.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Of conservation concern.

Rhododendron prunifolium is most closely related to R. flammeum, R. cumberlandense, and R. calendulaceum, and can be distinguished from all of those orange- to red-flowered species by its nearly glabrous and more gradually expanded corolla tube and by the indistinct nature of the floral blotch (K. A. Kron 1993). This species is federally protected.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Source FNA vol. 8, p. 462. FNA vol. 8, p. 470.
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. macrophyllum, R. maximum, R. minus, R. occidentale, R. periclymenoides, R. prinophyllum, R. prunifolium, R. tomentosum, R. vaseyi, R. viscosum
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. tomentosum, R. vaseyi, R. viscosum
Synonyms Azalea lapponica Azalea prunifolia
Name authority (Linnaeus) Wahlenberg: Fl. Lapp., 104. 1812 , (Small) Millais: Rhododendrons, 230. 1917 ,
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