Distributed from Newfoundland and Quebec, south to eastern Pennsylvania and northern New Jersey.
Global Range: The plant ranges from Newfoundland and Quebec west to Ontario, and south to eastern Pennsylvania and northern New Jersey.
Rhizomatous shrub to lm tall; bark reddish brown to grey, smooth to very slightly longitudinally grooved and flaking; young twigs pale to reddish brown, often with a pink tinge, usually glaucous, sparsely covered with multicellular eglandular and shorter gland-headed hairs, moderately to densely covered with short unicellular hairs; new foliage shoots arising from axillary buds associated with foliage leaves of previous year's shoot (i.e. below terminal bud), and some terminal buds. Vegetative bud scales moderately to densely unicellular-pubescent abaxially and often with scattered multicellular gland-headed and eglandular hairs, especially near apex or along midvein, moderately to densely unicellular-pubescent adaxially; margin fringed with unicellular hairs, the lowermost scales often with aristate apices or rudimentary blades. Leaves deciduous, dull bluish green (glaucous) to rarely dark green adaxially, pale to whitish green abaxially, turning red in autumn, alternate (with internodes becoming more closely spaced towards tip of shoot). Blade membranaceous to char-taceous, elliptic or oblong to obovate, 1-8.3 x0.4-3cm; base cuneate or acute to rounded, apex acute to rounded, usually with a short mucro; midvein strongly raised and prominent abaxially, the secondary veins flat to slightly raised abaxially; adaxial surface, including midvein, sparsely to moderately covered with short unicellular hairs and multicellular eglandular and gland-headed hairs; abaxial surface, including midvein and higher order veins, moderately to densely covered with short unicellular hairs and moderately covered with multicellular eglandular and gland-headed hairs, the eglandular hairs of midvein larger than those of higher order veins and lamina; margin entire, revolute to less commonly plane, fringed with multicellular eglandular hairs and with inconspicuous unicellular hairs; petiole l-12mm long, moderately to densely unicellular-pubescent, and with scattered multicellular eglandular and gland-headed hairs, the base of petiole slightly expanded at point of attachment. Flower buds terminal (rarely also from axillary buds just below terminal bud), larger than, but otherwise ± similar to, vegetative buds, more frequently densely unicellular-pubescent. Flowers appearing before or occasionally with the leaves; inflorescence an umbellate raceme of 3-9 flowers. Pedicels 3-10mm long, usually glaucous, usually sparsely covered with multicellular gland-headed hairs, and lacking to densely covered with unicellular hairs. Calyx lobes broadly subovate to triangular-ovate, 0.4-1.5 x 0.7-1.6mm; apex rounded; margin fringed with multicellular gland-headed and/or eglandular hairs, and unicellular hairs; adaxial surface glabrous; abaxial surface usually glaucous, glabrous to densely unicellular-pubescent, often with scattered multicellular gland-headed hairs. Corolla rose-purple to pink, or rarely white, unspotted to red-spotted on upper 3 lobes, fragrant, strongly zygomorphic, clearly 2-lipped due to the very extensive fusion of the upper 3 lobes contrasting with the 2 elongate and widely divergent lower lobes, the tube essentially lacking due to deep division between 2 lower lobes and between lateral and lower lobes; upper corolla lobe 0.3-0.8 x 0.25-0.5cm; lateral lobes 1.2-2.2 x 0.25-0.4cm (closely fused with upper lobe); lower lobes 1.2-2.2 x 0.25-0.6cm (± free); outer and inner surfaces of corolla glabrous to occasionally with few scattered multicellular gland-headed hairs. Stamens 10, slightly declinate to ± straight, variable in length, 0.9-2cm long, exserted (due to deeply cut corolla); filaments glabrous distally, becoming densely covered with flattened unicellular hairs proximally. Ovary L7-3mm long, densely covered with multicellular gland-headed and eglandular hairs and unicellular hairs; style slightly declinate, 1.1-2.2cm long, glabrous to unicellular-pubescent near base, often glaucous. Capsules ovoid to nearly cylindrical and curved near the base, slightly grooved, 0.7-1.7x0.3-0.6cm, often glaucous, moderately covered with multicellular gland-headed and eglandular hairs and densely covered with short unicellular hairs. Seeds brown, flattened ellipsoid, 1-2.7x0.4-1.3mm; testa tightly appressed to body, with cells at each end elongated and expanded, forming a flat tail 0.3-0.9mm long, the cells covering central portion of body elongate and non-bulging, those along margin expanded and flattened (in plane parallel to compression of seed body), forming an irregular wing-like fringe connecting the tails. Cotyledons lacking multicellular hairs and with venation represented by rnidvein and one (or very few) poorly developed secondary veins. 2´ = 52 (Sax, 1930).
Comments: A shrub that may form dominant stands or only a few scattered stems in wetlands of acidic rocky summits and barrens, as well as boggy habitats containing a mixture of organic material and gravel (New York Natural Heritage Program 2004). Bogs and wet woods (Gleason and Cronquist 1991). Bogs, damp thickets, acid barrens and rocky summits and slopes (Fernald 1970).
In moist to dry coniferous or deciduous forests, thickets, open rocky areas, lake margins, bogs, and swamps
Number of Occurrences
Note: For many non-migratory species, occurrences are roughly equivalent to populations.
Estimated Number of Occurrences: > 300
Molecular Biology and Genetics
Barcode data: Rhododendron canadense
Statistics of barcoding coverage: Rhododendron canadense
Public Records: 1
Specimens with Barcodes: 4
Species With Barcodes: 1
National NatureServe Conservation Status
Rounded National Status Rank: NNR - Unranked
Rounded National Status Rank: NNR - Unranked
NatureServe Conservation Status
Rounded Global Status Rank: G5 - Secure
Environmental Specificity: Moderate. Generalist or community with some key requirements scarce.
Global Short Term Trend: Relatively stable (=10% change)
Global Long Term Trend: Increase of 10-25% to decline of 30%
Degree of Threat: Low
Today's botanists consider the rhodora to be a distant relative of the other North American members of its genus, but the difference in floral structure did lead 19th century taxonomists to assign the plant its own genus Rhodora. Its closest relative is Rhododendron vaseyi from the Appalachian Mountains, which differs in having 7 stamens.
It reaches a mature height of 0.5-1.2 m (approximately 1-3 feet). In early spring, it produces pinkish-purple flowers in clusters of 2-6 together; each flower is 2-3 cm (approximately 1 inch) in diameter, with a five-lobed purple corolla. The flowers are unusual in comparison with other species of the genus Rhododendron found in northeastern North America. Most rhododendrons of the region have tubular flowers with 5 stamens each, while R. canadense has 10 stamens housed inside a zygomorphic corolla. The leaves open only after the flowers have bloomed and wilted; they are narrow oval, 2-6 cm long and 1-2 cm broad. When not in flower, it can still be identified by its peculiar, orange-brown seed cases, 1-1.2 cm long.
Distribution and habitat
The wild distribution of the rhodora begins at its easternmost extreme in Canada in Newfoundland and extends into eastern Ontario and the United States, where it has its most famous home in New England and also occurs naturally in New York, New Jersey, and at high altitudes in the Appalachian Mountains further south to Pennsylvania. It thrives in the moist, acidic soils of bogs, swamps, and clearings in woodlands.
For a long time, the species was regarded as a botanical icon of New England. The Transcendtalist writer Ralph Waldo Emerson, who spent his life in Concord, Massachusetts, paid homage to it in his poem "The Rhodora: On being asked, Whence is the flower?" (1834, pub. 1847). In this reflective lyric, the poet arrives at the epiphany that the beauty of the rhodora exists not only for its own sake but also discloses the mystical unity of all creation under God. The poet embraces this unity in his parting words to the rhodora: "The self-same Power that brought me there brought you". The composer Mary Lynn Lightfoot later set the poem to music in a song of the same name for a women's choir.
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