Rhododendron canadense

(L.) Torr.

Rhodora

G5Secure Found in 16 roadless areas NatureServe Explorer →
G5SecureGlobal Rank
UnknownThreat Impact
Identity
Unique IDELEMENT_GLOBAL.2.128779
Element CodePDERI15090
Record TypeSPECIES
ClassificationSpecies
Classification StatusStandard
Name CategoryVascular Plant
Endemicoccurs (regularly, as a native taxon) in multiple nations
KingdomPlantae
PhylumAnthophyta
ClassDicotyledoneae
OrderEricales
FamilyEricaceae
GenusRhododendron
Other Common Names
Rhododendron du Canada (FR) rhodora (EN)
Concept Reference
Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
Conservation Status
Rank Method Rank calculation - Biotics v2
Review Date2025-08-20
Change Date1984-08-29
Edition Date2025-08-20
Edition AuthorsWeldy, Troy W. (2005), rev. N. Ventrella (2025)
Threat ImpactUnknown
Range Extent200,000-2,500,000 square km (about 80,000-1,000,000 square miles)
Number of Occurrences> 300
Rank Reasons
Rhododendron canadense is a woody shrub occurring in mixed or conifer forests, rocky areas, lake margins, bogs, and swamps of eastern North America, from Ontario east to Newfoundland and Labrador, Canada, south to New Jersey and Pennsylvania in the United States. There are over 1,000 estimated occurrences of this taxon, which are potentially threatened by development, water diversion, alteration of hydrology, recreational activities, rights-of-way construction and maintenance, invasive species, succession, and other threats in some places. Little is known about threats and trends, but with a large range extent, high number of occurrences, abundant habitat, and broad habitat preferences, Rhododendron canadense is considered secure.
Range Extent Comments
Rhododendron canadense occurs in eastern North America, from Ontario east to Newfoundland and Labrador, Canada, south to New Jersey and Pennsylvania in the United States (FNA 2009). Range extent was estimated to be just over 1.1 million square kilometers using herbarium specimens, photo-based observations, and NatureServe Network occurrence data collected between 1994 and 2025 (GBIF 2025, iNaturalist 2025, NatureServe 2025, RARECAT 2025, SEINet 2025).
Occurrences Comments
By applying a 1 km separation distance to herbarium specimens, photo-based observations, and NatureServe Network occurrence data documented between 1994 and 2025, it is estimated that there are more than 1,000 occurrences rangewide (GBIF 2025, iNaturalist 2025, NatureServe 2025, RARECAT 2025, SEINet 2025).
Threat Impact Comments
Threats to Rhododendron canadense are not well known, but likely include development, water diversion, alteration of hydrology, recreational activities, rights-of-way construction and maintenance, invasive species, succession, and other threats in some places, though there is insufficient data, including anecdotal accounts, to understand scope and severity of threats for this species.
Ecology & Habitat

Description

Rhodora is a woody shrub with ascending branches that only grows up to 1.5 meters tall. It can be seen as a single shrub or in small to very large colonies. The flowers appear when the leaves are just expanding. Each branch is topped by a cluster of four or five deep rose colored flowers with long stamens sticking out. The three main petals are divided nearly to the white-colored base and the upper petal has three lobes on the top. Since there is no flower tube the flower appears very open. The oval, deciduous leaves are 2-5 cm long, fuzzy underneath, and mainly at the ends of the branches. The dry woody fruits are whitish, fuzzy, and split open along the sides into five sections.

Habitat

Rhododendron canadense occurs in "moist to dry, coniferous or mixed conifer-deciduous forests, thickets, open rocky areas, lake margins, bogs, [and] swamps" from 0-1900 m in elevation (FNA 2009). This species can be found on acid barrens and rocky summits and slopes, as well as in boggy habitats containing a mixture of organic material and gravel (Fernald 1970, Gleason and Cronquist 1991, New York Natural Heritage Program 2009).

Ecology

This species is the host plant for the Columbia silkmoth (Hyalophora columbia) (Native Plant Trust 2025).
Terrestrial Habitats
Forest - ConiferForest - MixedBarrensBare rock/talus/scree
Palustrine Habitats
FORESTED WETLANDBog/fen
Other Nations (2)
CanadaN5
ProvinceRankNative
OntarioS1Yes
LabradorSUYes
QuebecS4Yes
Nova ScotiaS5Yes
Prince Edward IslandS5Yes
New BrunswickS5Yes
Island of NewfoundlandS5Yes
United StatesN5
ProvinceRankNative
ConnecticutS3Yes
MassachusettsSNRYes
New YorkS2Yes
New HampshireSNRYes
Rhode IslandS2Yes
MaineSNRYes
PennsylvaniaSNRYes
New JerseyS1Yes
VermontS4Yes
Threat Assessments
ThreatScopeSeverityTiming
Unknown/undetermined

Plant Characteristics
DurationPERENNIAL
Economic Value (Genus)No
Roadless Areas (16)
Maine (1)
AreaForestAcres
Caribou - Speckled ExtWhite Mountain National Forest5,988
New Hampshire (13)
AreaForestAcres
Cherry MountainWhite Mountain National Forest8,766
Dartmouth RangeWhite Mountain National Forest9,233
Great Gulf Ext.White Mountain National Forest15,110
KearsargeWhite Mountain National Forest4,554
KilkennyWhite Mountain National Forest28,766
Kinsman MountainWhite Mountain National Forest8,999
Mt. Wolf - Gordon PondWhite Mountain National Forest11,846
PemigewassetWhite Mountain National Forest32,255
Pemigewasset ExtWhite Mountain National Forest15,840
Presidential - Dry River ExtWhite Mountain National Forest10,555
Sandwich RangeWhite Mountain National Forest16,797
WatervilleWhite Mountain National Forest4,312
Wild RiverWhite Mountain National Forest46,878
Vermont (2)
AreaForestAcres
Devil's Den 09083Green Mountain and Finger Lakes National Forests9,169
Lye Brook Addition 09085Green Mountain and Finger Lakes National Forests1,111
References (12)
  1. Dodds, J.S. 2023. <i>Rhododendron canadense</i> Rare Plant Profile. New Jersey Department of Environmental Protection, State Parks, Forests & Historic Sites, State Forest Fire Service & Forestry, Office of Natural Lands Management, New Jersey Natural Heritage Program, Trenton, NJ. 18 pp. [https://www.state.nj.us/dep/parksandforests/natural/heritage/docs/rhododendron-canadense-rhodora.pdf]
  2. Fernald, M.L. 1970. Gray's manual of botany. 8th edition. 1970 printing with corrections by R.C. Rollins [of 1950 8th edition]. D. Van Nostrand Company, New York.
  3. Flora of North America Editorial Committee (FNA). 2009. Flora of North America north of Mexico. Vol. 8. Magnoliophyta: Paeoniaceae to Ericaceae. Oxford University Press, New York. xxiv + 585 pp.
  4. Gleason, H.A., and A. Cronquist. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. New York Botanical Garden, Bronx, New York. 910 pp.
  5. Global Biodiversity Information Facility (GBIF). 2025. Global Biodiversity Information Facility (GBIF) data portal. Online. Available: https://www.gbif.org/ (accessed 2025).
  6. iNaturalist. 2025. Online. Available: https://www.inaturalist.org (accessed 2025).
  7. Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
  8. Native Plant Trust. 2025. Go Botany website. Online. Available: https://gobotany.nativeplanttrust.org (accessed 2025).
  9. NatureServe. 2025. NatureServe Network Biodiversity Location Data. NatureServe, Arlington, Virginia.
  10. New York Natural Heritage Program. 2009. Jan 15 last update. Online Conservation Guide for <i>Rhododendron canadense</i>. Online. Available: https://guides.nynhp.org/rhodora/(accessed 2025).
  11. <p>NatureServe's Rapid Analysis of Rarity and Endangerment Conservation Assessment Tool (RARECAT). 2025. Version: 2.1.1 (released April 04, 2025).</p>
  12. Southwest Environmental Information Network (SEINet). 2025. Collections Databases. Online. Available: https://swbiodiversity.org/seinet/collections/index.php (accessed 2025).