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great laurel, great rosebay, rhododendron, rosebay, rosebay rhododendron

Canada rosebay, rhodora

Habit Shrubs or trees, to 10 m, sometimes rhizomatous. Shrubs, to 1 m, rhizomatous.
Stems

bark smooth to vertically furrowed, shredding;

twigs multicellular stipitate-glandular-hairy and eglandular-hairy (hairs basally branched, crisped/matted), glabrate in age.

bark ± smooth to slightly shredding;

twigs sparsely multicellular eglandular- and shorter stipitate-glandular-hairy (hairs unbranched), also unicellular-hairy.

Leaves

persistent;

petiole multicellular-hairy (hairs ± branched), often glabrescent;

blade oblong to obovate or elliptic, (6–)9–20(–31) × (1.5–)2–5(–8) cm (length/width ratio 2.4–8), thick, coriaceous, margins entire, revolute to ± plane, glabrous or sparsely hairy (hairs branched), apex acuminate to sometimes acute, surfaces scattered stipitate-glandular-hairy and eglandular-hairy (hairs forming dense mat, basally branched, crisped, abaxially becoming sticky and matted, forming ± scaly or continuous, pale, shellaclike coating, smooth to slightly roughened, hairs ± deciduous adaxially).

deciduous;

petiole multicellular eglandular- and stipitate-glandular-hairy and unicellular-hairy;

blade elliptic to oblong or obovate, 1–8.3 × 0.4–3 cm, thin, membranous to chartaceous, margins entire, usually ± revolute, sometimes plane, eglandular- and unicellular-hairy, apex acute to rounded, abaxial surface eglandular- and stipitate-glandular-hairy, also unicellular-hairy, (± glaucous), adaxial surface scattered eglandular- and stipitate-glandular-hairy, also unicellular-hairy.

Inflorescences

10–25-flowered;

bracts similar to bud scales.

sometimes fasciculate, 3–9-flowered;

bracts similar to bud scales.

Pedicels

17–60 mm, multicellular stipitate-glandular-hairy.

3–10 mm, (usually glaucous), usually sparsely stipitate-glandular-hairy, and sometimes also densely unicellular-hairy.

Flowers

opening after development of leaves (of flowering shoots), erect to horizontal, not or only slightly fragrant;

calyx lobes 2–6 mm, stipitate-glandular-hairy;

corolla white to pink, rarely deep pink to purple, with yellowish green spots on upper lobe, campanulate, 20–36 mm, scattered stipitate-glandular-hairy on outer surface, petals connate, lobes 10–23 mm, tube gradually expanding into lobes, 7–16 mm;

stamens 10, included, ± unequal, 14–26 mm; (ovary stipitate-glandular-hairy).

appearing before or, sometimes, with leaves, erect to horizontal, fragrant;

calyx lobes 0.4–1.5 mm, often scattered stipitate-glandular-hairy, sometimes also unicellular-hairy, margins glandular- and/or eglandular-ciliate;

corolla rose-purple to pink, rarely white, unspotted or red-spotted on upper 3 lobes, irregularly shaped, clearly 2-lipped due to very extensive connation of 3 upper lobes contrasting with 2 elongate, widely divergent lower lobes, 12–22 mm, glabrous or, sometimes, sparsely stipitate-glandular-hairy on outer surface, petals connate, upper lobe 3–8 mm, lateral lobes 12–22 mm (closely connate with upper lobe), lower lobes 12–22 mm, tube absent due to deep division between 2 lower lobes and between lateral and lower lobes;

stamens 10, exserted, ± unequal, 9–20 mm.

Capsules

borne on erect pedicels, 8–20 × 4–6.5 mm, stipitate-glandular-hairy.

borne on erect pedicels, 0.7–1.7 × 0.3–0.6 mm, multicellular stipitate-glandular- and eglandular-hairy and densely unicellular-hairy.

Seeds

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

testa expanded, dorsiventrally flattened, loose.

with flattened tails;

testa tightly appressed.

Floral

bud scales stipitate-glandular-hairy, eglandular-hairy (hairs ferruginous, crisped), and short unicellular-hairy abaxially, margins hairy (hairs branched, long-celled).

bud scales unicellular-hairy abaxially, and often stipitate-glandular- and eglandular-hairy, margins unicellular-hairy.

2n

= 26.

= 52.

Rhododendron maximum

Rhododendron canadense

Phenology Flowering summer. Flowering spring.
Habitat Stream banks, mesic woods Moist to dry, coniferous or mixed conifer-deciduous forests, thickets, open rocky areas, lake margins, bogs, swamps
Elevation 0-1900 m (0-6200 ft) 0-1900 m (0-6200 ft)
Distribution
from FNA
AL; CT; GA; KY; MA; MD; ME; NC; NH; NJ; NY; OH; PA; RI; SC; TN; VA; VT; WV
[WildflowerSearch map]
[BONAP county map]
from FNA
CT; MA; ME; NH; NJ; NY; PA; RI; VT; NB; NF; NS; ON; PE; QC
[WildflowerSearch map]
[BONAP county map]
Discussion

Individuals of Rhododendron maximum are beautiful, cold-hardy shrubs and are frequently cultivated as ornamentals. Hybrids with R. catawbiense occur. This species has been attributed in standard floras to eastern Canada but not confirmed there by specimens.

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

Rhododendron canadense is distinctive and is most closely related to R. vaseyi; together they constitute sect. Rhodora (Linnaeus) G. Don (W. S. Judd and K. A. Kron 1995). Rhododendron canadense is sometimes cultivated for its showy flowers.

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

Source FNA vol. 8, p. 463. FNA vol. 8, p. 464.
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. 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. 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. prunifolium, R. tomentosum, R. vaseyi, R. viscosum
Synonyms R. ashleyi Rhodora canadensis
Name authority Linnaeus: Sp. Pl. 1: 392. 1753 , (Linnaeus) Torrey: in New York State, Rep. Geol. Surv., 151. 1841 ,
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