The green links below add additional plants to the comparison table. Blue links lead to other Web sites.
enable glossary links

Piedmont rhododendron

mountain azalea, Piedmont or southern pinxterbloom azalea

Habit Shrubs, to 3(–5) mm, often rhizomatous. Shrubs or trees, to 6 m, usually not rhizomatous.
Stems

bark smooth to vertically furrowed, shredding;

twigs with ferrugineous, multicellular, broad-rimmed, glandular-peltate scales.

bark smooth to vertically furrowed, shredding;

twigs scattered, multicellular eglandular- and/or stipitate-glandular-hairy (hairs unbranched), otherwise moderately to densely unicellular-hairy.

Leaves

persistent;

petiole with ferruginous, broad-rimmed, glandular-peltate scales and unicellular-hairy;

blade narrowly elliptic to elliptic or oval, sometimes obovate, (1–)5–8(–13) × (1–)2–3.5(–5.5) cm, thick, coriaceous, margins entire, plane to conspicuously revolute, with scattered, glandular-peltate scales, apex acute or acuminate or obtuse to rounded, surfaces with scattered, ferruginous, broad-rimmed, glandular-peltate scales abaxially, (scales ± deciduous adaxially).

deciduous;

petiole usually multicellular eglandular- or stipitate-glandular-hairy, also unicellular-hairy;

blade ovate to obovate, 2.5–10(–13) × 1.2–3(–4) cm, thin, membranous to chartaceous, margins entire, rarely minutely serrulate, plane, inconspicuously ciliate, eglandular-hairy (hairs appressed to margins), apex acute to obtuse, often mucronate, abaxial surface densely to sparsely unicellular-hairy, sometimes glabrous or glabrate, often also scattered eglandular-hairy, adaxial surface usually scattered eglandular-hairy, otherwise sparsely unicellular-hairy, sometimes glabrous.

Inflorescences

5–10-flowered;

bracts similar to bud scales.

6–19-flowered;

bracts similar to bud scales.

Pedicels

5–15 mm, with ferruginous scales.

4–17 mm, usually eglandular-hairy, rarely stipitate-glandular- and/or eglandular-hairy, otherwise sparsely to densely unicellular-hairy.

Flowers

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

calyx lobes 0.5–2 mm, with ferruginous scales;

corolla dark to very pale pink or white, upper lobe usually with greenish spots, campanulate to funnelform, 15–37 mm, with scattered, ferruginous, peltate scales on outer surface, petals connate (for 3/4+ their lengths), lobes 8–19 mm, tube gradually expanding into lobes, 8–22 mm;

stamens 10, included to slightly exserted, ± unequal, 13–26 mm.

opening before or with leaves, erect to horizontal, fragrant (usually musky-scented);

calyx lobes 0.5–4 mm, surfaces and margins scattered stipitate-glandular- and/or eglandular-hairy, otherwise usually densely unicellular-hairy;

corolla deep pink to white with pink tube, without blotch on upper lobe, funnelform, 23–46 mm, scattered, multicellular stipitate-glandular-hairy (hairs not forming distinct lines), otherwise sparsely to densely unicellular-hairy on outer surface, petals connate, lobes 7–20 mm, tube ± gradually expanded into lobes, 13–27 mm (equaling or longer than lobes);

stamens 5, much exserted, ± unequal, 31–64 mm.

Capsules

borne on erect pedicels, 6–14 × 2.9–5 mm, with ferruginous, peltate scales.

borne on erect pedicels, 12–33 × 3–6.5 mm, usually sparsely to moderately eglandular-hairy, otherwise ± densely unicellular-hairy.

Seeds

with short, blunt/truncate tails at each end;

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 unicellular-ciliate.

bud scales ± densely unicellular-hairy abaxially, margins usually unicellular-ciliate.

2n

= 26.

= 26.

Rhododendron minus

Rhododendron canescens

Phenology Flowering spring.
Habitat Moist to dry woods, pocosins, swamps and savannas, often along streams
Elevation 0-500 m (0-1600 ft)
Distribution
from FNA
AL; FL; GA; NC; SC; TN
[WildflowerSearch map]
[BONAP county map]
from FNA
AL; AR; FL; GA; IL; KY; LA; MS; NC; OK; SC; TN; TX
[WildflowerSearch map]
[BONAP county map]
Discussion

Varieties 2 (2 in the flora).

Rhododendron minus is here circumscribed broadly, including R. carolinianum and R. chapmanii, and the latter is considered to be a distinct variety (W. H. Duncan and T. M. Pullen 1962). Variety chapmanii is federally listed. This species is often grown as an ornamental.

Rhododendron minus and R. lapponicum are members of subg. Rhododendron, as indicated by their glandular-peltate scales; the subgenus is represented by hundreds of species in eastern and southern Asia (see J. Cullen 1980).

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

Rhododendron canescens is most similar to R. prinophyllum and R. periclymenoides, although these three species do not constitute a clade (K. A. Kron 1993); they occasionally hybridize where their habitats and ranges overlap. In addition, putative hybrids with R. alabamense, R. atlanticum, R. austrinum, R. flammeum, R. periclymenoides, and R. calendulaceum are known.

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

Key
1. Leaf blades: apex usually acute or acuminate; petioles (5-)6-20 mm; branches not rigidly ascending.
var. minus
1. Leaf blades: apex usually rounded or obtuse; petioles 2-6(-7) mm; branches usually rigidly erect-ascending
var. chapmanii
Source FNA vol. 8, p. 460. FNA vol. 8, p. 469.
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. lapponicum, R. macrophyllum, R. maximum, 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. 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. prunifolium, R. tomentosum, R. vaseyi, R. viscosum
Subordinate taxa
R. minus var. chapmanii, R. minus var. minus
Synonyms Azalea canescens, Azalea candida
Name authority Michaux: J. Hist. Nat. 1: 412. 1792 , (Michaux) Sweet: Hort. Brit. ed. 2, 343. 1830 ,
Web links