This Rhododendron is fairly hard to grow since it needs just the right amount of moisture, always moist but not too wet. It is usually pollinated by female bumblebees. It looked so different from other rhododendrons that it was at one time put in the genus Rhodora, hence the common name. Rhodora is also the name of the botanical journal published by the New England Botanical Club.
There are approximately eight known populations, and some of these have hundreds to thousands of stems. Many of these populations are within protected landscapes. Today there are few threats on these populations and the short/long term trends appear stable.
Current evidence indicates that the short-term trend has been stable and there is no reason to believe this will change anytime in the near future.
This plant was never known from more than 10 localities in New York and there are now the same number of occurrences as were known historically.
The plants are isolated enough that threats are low to insignificant.
There are no management needs at this time.
There are no research needs at this time.
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).
A showy flowering shrub located in the St. Lawrence Valley, Adirondacks, Rensselaer Plateau, and the Shawangunk Mountains. Some of our largest populations are located in the Shawangunks. New York is at the western edge of its range.
The plant ranges from Newfoundland and Quebec west to Ontario, and south to eastern Pennsylvania and northern New Jersey.
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.
This shrub, up 1.5 meters tall, has strongly ascending branches and deciduous leaves. The inflorescences are mostly expanded before leaves. The pale pink to deep rose-purple corolla is strongly irregular with a short (to no) corolla tube. Each flower has 10 stamens with a 1.5-2 cm long style. The capsules are 0.7-1.5 cm long and glaucous-puberulent. The leaves are oblong-elliptic, blunt, and closely pubescent (rarely glaucous) beneath.
While this shrub can be identified from fruit, flowers make it very easy to see and identify.
If observed in flower, this shrub is unique among Rhododendron species and not likely confused.
This shrub flowers mid-May to mid-June. According to the records of Daniel Smiley, the Shawangunk plants typically flower around May 21st. The fruit capsules may persist on the shrub indefinitely, but the seeds generally disperse by late fall. The ideal survey time is late May, when this shrub is likely in bloom.
The time of year you would expect to find Rhodora vegetative, flowering, and fruiting in New York.
Rhododendron canadense (L.) Torr.
Gleason, Henry A. and A. Cronquist. 1991. Manual of Vascular Plants of Northeastern United States and Adjacent Canada. The New York Botanical Garden, Bronx, New York. 910 pp.
Fernald, M.L. 1950. Gray's manual of botany. 8th edition. D. Van Nostrand, New York. 1632 pp.
Holmgren, Noel. 1998. The Illustrated Companion to Gleason and Cronquist's Manual. Illustrations of the Vascular Plants of Northeastern United States and Adjacent Canada. The New York Botanical Garden, Bronx, New York.
Mitchell, Richard S. and Gordon C. Tucker. 1997. Revised Checklist of New York State Plants. Contributions to a Flora of New York State. Checklist IV. Bulletin No. 490. New York State Museum. Albany, NY. 400 pp.
New York Natural Heritage Program. 2010. Biotics database. New York Natural Heritage Program. New York State Department of Environmental Conservation. Albany, NY.
New York Natural Heritage Program. 2020. New York Natural Heritage Program Databases. Albany, NY.
Reschke, Carol. 1990. Ecological communities of New York State. New York Natural Heritage Program, New York State Department of Environmental Conservation. Latham, NY. 96 pp. plus xi.
Weldy, T. and D. Werier. 2010. New York flora atlas. [S.M. Landry, K.N. Campbell, and L.D. Mabe (original application development), Florida Center for Community Design and Research http://www.fccdr.usf.edu/. University of South Florida http://www.usf.edu/]. New York Flora Association http://newyork.plantatlas.usf.edu/, Albany, New York
Information for this guide was last updated on: January 15, 2009
Please cite this page as:
New York Natural Heritage Program. 2020. Online Conservation Guide for Rhododendron canadense. Available from: https://guides.nynhp.org/rhodora/. Accessed September 21, 2020.