The species name "nephrophylla" means kidney-leaf, and refers to the shape of the basal leaves. Like most violets, this species produces "cleistogamous", meaning closed flowers as well as the familiar purple violet blossoms. These easily overlooked cleistogamous flowers never open and have no petals, and look like small bumps on the stems. They produce seeds by self-fertilization.
There are only 4 verified occurrences and 7 historical occurrences known from New York. Only 2 of the verified occurrences are ranked as better than "fair". The historical occurrences date from the early 1900s, and most sites have never been re-checked.
More precise population data are needed to determine trends for this species, though none of the verified occurrences are known to have been extirpated or have undergone declines in recent years.
The long-term trend for this species is unclear; there are sixteen historical occurrences that should be searched for.
Trampling and erosion by human activity, and trampling and herbivory by deer, have been identified as threats to some of the known populations.
Trails and human activity should be directed away from populations to prevent trampling. Some sites may need management to maintain an open aspect.
In New York Viola nephrophylla has been collected from a variety of cold, wetland habitats, including open marl fens within larger swamps, Northern White-cedar swamps and wet pastures. It also occupies calcareous shoreline outcrops and boreal heath barrens (New York Natural Heritage Program 2008). Gravelly (often calcareous) shores, slopes, bogs and open low grounds (Fernald 1970). Mainly in the western cordillera, but extending east in cold, wet places (often in a high pH) (Gleason and Cronquist 1991). Circumneutral soils of fens, ledges, and peaty shores (Haines and Vining 1998).
Viola nephrophylla is known from scattered locations in the western and northern parts of the state.
Viola nephrophylla is a perennial wildflower species. Its leaves are hairless, and wider than long, with roughly kidney-shaped bases. It is a "stemless" species, the flowers borne singly on leafless stalks emerge directly from the base of the plants. In Viola nephrophylla the flowering stalks extend much above the flowers. The petals are blue, the bottom and two adjacent ones densely "bearded" with threadlike hairs. The sepals are short, and obtuse to rounded at the apex. Like most other violets V. nephropylla also produces cleistogamous, or petal-less flowers, held on separate, erect basal stalks. The fruit are green, short, egg-shaped capsules, holding green-black seeds.
Viola sororia has leaves moderately to densely hairy throughout, and flowers as tall as or barely exceeding the leaves, and it is a plant of common upland habitats, while V. nephrophylla is most often found in cold, calcareous wetlands. Viola cucullata, Marsh Blue Violet, has a hairless bottom petal and long-tapering sepals with acute apices, and is a plant of circumneutral to acidic wetlands (Ballard 1994).
Viola nephrophylla flowers from mid-April to early June, and the fruits may persist into September.
The time of year you would expect to find Northern Bog Violet vegetative, flowering, and fruiting in New York.
Northern Bog Violet
Viola nephrophylla Greene
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Fernald, M.L. 1950. Gray's manual of botany. 8th edition. D. Van Nostrand, New York. 1632 pp.
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Haines, A. and T.F. Vining. 1998. Flora of Maine, A Manual for Identification of Native and Naturalized Vascular Plants of Maine. V.F.Thomas Co., Bar Harbor, Maine.
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New York Natural Heritage Program. 2023. New York Natural Heritage Program Databases. Albany, NY.
Newcomb, Lawrence. 1977. Newcomb's Wildflower Guide: An Ingenious New Key System for Quick, Positive Field Identification of the Wildflowers, Flowering Shrubs, and Vines of Northeastern and North-Central North America. Little, Brown and Company. Boston.
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 5, 2009
Please cite this page as:
New York Natural Heritage Program. 2023. Online Conservation Guide for Viola nephrophylla. Available from: https://guides.nynhp.org/northern-bog-violet/. Accessed March 31, 2023.