A characteristic species found in freshwater intertidal marshes is wild rice (Zizania aquatica). In addition to providing habitat and food for fish and waterfowl, wild rice has been an important food staple for Native Americans for thousands of years. The ancestral grain to wild rice has even been found in layers of earth dating back 12,000 years! Today, about 23 million pounds of "wild" wild rice varieties as well as "cultivated" wild rice varieties are produced each year around the world - 4 million of which is considered "wild" grow.
This community is restricted to the freshwater portion of tidal rivers. The majority of occurrences are on the Hudson River with over 75% in Greene, Columbia, and Dutchess Counties. There are estimated to be about 40 occurrences in the state. Several of these occurrences are threatened because of shoreline development and invasive plants.
The number of freshwater tidal marshes in New York have probably remained stable in recent decades due to wetland protectection regulations. However, the condition and size of a few occurrences may have declined due to invasive species, such as purple loosestrife (Lythrum salicaria) and reed grass (Phragmites australis ssp. australis).
The number of freshwater tidal marshes in New York probably declined substantially from historical numbers as a result of shoreline development (e.g., railroads) and river channel dredging.
The main threats to this community are shoreline development (e.g., railroad tracks that impede or alter tidal flow), and invasion of exotic species, such as purple loosestrife (Lythrum salicaria) and reed grass (Phragmites australis ssp. australis). A lesser threat is chemical run-off from railroad maintance or accidental spill. Dredging of shipping lanes may also pose a threat by reducing water quality, or decreasing area due to depositon of dredge spoils.
Maintain tidal regime in marshes cut off from the Hudson River by the railroad tracks. Control and remove invasive exotic species, such as purple loosestrife (Lythrum salicaria) and reed grass (Phragmites australis ssp. australis).
Strive to minimize or eliminate hardened shorelines and maintain very low-sloped shorelines within the tidal zone. Maintain high connectivity between the river and bays with marshes to encourage full tidal flushing during each cycle of the tides. For example, barriers such as railway causeways should have numerous culverts to allow sufficient hydrologic connectivity.
Review tidal marsh maps and data collected by partner organizations and incorporate this information into the New York Natural Heritage database. Resurvey and update occurrences with records greater than 10 years old.
Research the effects of invasive exotic plants on freshwater tidal marshes.
This community is currently restricted to the central Hudson Valley portion of the Hudson River, ranging from Rensselaer County to Rockland County, with most occurring in Columbia, Green, Dutchess, and Ulster Counties. Small examples of freshwater tidal marsh also occur along tidal rivers on Long Island.
Freshwater tidal marshes occur along tidal rivers on the Atlantic Coastal Plain from Maine to North Carolina.
A marsh community that occurs in shallow bays, shoals, and at the mouth of tributaries of large tidal river systems, where the water is usually fresh (with salinity less than 0.5 parts per thousand), and less than 2 m (6 feet) deep at high tide. The vegetation is dominated by aquatics that are emergent at high tide. Typically there are two zones in a freshwater tidal marsh: a low-elevation area dominated by short, broad-leaved emergents bordering mudflats or open water, and a slightly higher-elevation area dominated by tall graminoids.
Typical low-marsh examples are dominated by broad-leaved emergent plants, such as spatterdock (Nuphar advena), that are often mud- or silt-coated from two daily tidal deposits. Other examples have plants similar to those in shallow emergent marshes and can be quite diverse, but the tidal influence should be evident.
Known examples of this community have been found at elevations between -1 feet and 20 feet.
Freshwater tidal marshes are an excellent place to see wading birds throughout the summer. In the lower marshes, spatterdock has showy yellow flowers in mid-summer. Flocking birds feed on and help scatter wild rice and other seeds in the upper marshes in late summer and early fall.
This New York natural community encompasses all or part of the concept of the following International Vegetation Classification (IVC) natural community associations. These are often described at finer resolution than New York's natural communities. The IVC is developed and maintained by NatureServe.
This New York natural community falls into the following ecological system(s). Ecological systems are often described at a coarser resolution than New York's natural communities and tend to represent clusters of associations found in similar environments. The ecological systems project is developed and maintained by NatureServe.
Heteranthera reniformis (mud-plantain)
Impatiens capensis (spotted jewelweed, spotted touch-me-not)
Iris versicolor (blue flag)
Leersia oryzoides (rice cut grass)
Peltandra virginica (green arrow-arum, tuckahoe)
Pontederia cordata (pickerelweed)
Sagittaria latifolia (common arrowhead)
Sagittaria subulata (awl-leaved arrowhead)
Typha angustifolia (narrow-leaved cat-tail)
This figure helps visualize the structure and "look" or "feel" of a typical Freshwater Tidal Marsh. Each bar represents the amount of "coverage" for all the species growing at that height. Because layers overlap (shrubs may grow under trees, for example), the shaded regions can add up to more than 100%.
DeVries, C. and C.B. DeWitt. 1986. Freshwater tidal wetlands community description and relation of plant distribution to elevation and substrate. In: Polgar Fellowship Reports of the Hudson River National Estuarine Sanctuary Program 1986. E.A. Blair and J.C. Cooper, editors. Hudson River Foundation, New York, New York.
Edinger, G. J., D. J. Evans, S. Gebauer, T. G. Howard, D. M. Hunt, and A. M. Olivero (editors). 2014. Ecological Communities of New York State. Second Edition. A revised and expanded edition of Carol Reschke’s Ecological Communities of New York State. New York Natural Heritage Program, New York State Department of Environmental Conservation, Albany, NY. https://www.nynhp.org/ecological-communities/
Edinger, Gregory J., D.J. Evans, Shane Gebauer, Timothy G. Howard, David M. Hunt, and Adele M. Olivero (editors). 2002. Ecological Communities of New York State. Second Edition. A revised and expanded edition of Carol Reschke's Ecological Communities of New York State. (Draft for review). New York Natural Heritage Program, New York State Department of Environmental Conservation. Albany, NY. 136 pp.
Findlay, S.E.G., E. Kiviat, W.C. Nieder, and E.A. Blair. 2002. Functional assessment of a reference wetland set as a tool for science, management and restoration. Aquat. Sci. 64:107-117.
Kiviat, E. 1974. A fresh-water tidal marsh on the Hudson, Tivoli North Bay. Paper 14, In Third Symposium on Hudson River Ecology, Hudson River Environmental Society, Bronx, New York.
Kiviat, E. 1979. Hudson River Estuary shore zone: ecology and management. MA Thesis, State University College, New Paltz, New York.
Kiviat, E. and E. Beecher. 1991. Vegetation in the fresh-tidal habitats of Tivoli Bays, Hudson River. Hudsonia Ltd., Bard College Field Station, Annandale, New York.
Kiviat, Erik and Gretchen Stevens. 2001. Biodiversity assessment manual for the Hudson River Estuary Corridor. New York State Department of Environmental Conservation. Albany, NY.
Leck, A.L., R.L. Simpson, D.F. Whigham, and C.F. Leck. 1988. Plants of the Hamilton Marshes: A Delaware River freshwater tidal wetland. Bartonia 54:1-17.
MacDonald, Dana and Gregory Edinger. 2000. Identification of reference wetlands on Long Island, New York. Final report prepared for the Environmental Protection Agency, Wetland Grant CD992436-01. New York Natural Heritage Program, New York State Department of Environmental Conservation. Latham, NY. 106 pp. plus appendices.
Metzler, K. and R. Rosza. 1982. Vegetation of fresh and brackish tidal marshes in Connecticut. Newsletter of the Connecticut Botanical Society 10(1): 1-3.
Muenscher, W.C. 1937. VII. Aquatic vegetation of the Lower Hudson area. 1936. Biological Survey. 11:231-248.
New York Natural Heritage Program. 2023. New York Natural Heritage Program Databases. Albany, NY.
Odum, W.E., T.J. Smith III, J.K. Hoover, and C.C McIvor. 1984. The ecology of tidal freshwater marshes of the United States east coast: A community profile. U.S. Fish and Wildlife Service, Washington, D.C. FWS/OBS-83/17.
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.
Swift, Bryan L. 1987. An analysis of avian breeding habitats in Hudson River Tidal Marshes. New York State Department of Environmental Conservation, The Hudson River Foundation for Science and Environmental Research, Inc. 62 pp.
Information for this guide was last updated on: October 2, 2020
Please cite this page as:
New York Natural Heritage Program. 2023. Online Conservation Guide for Freshwater tidal marsh. Available from: https://guides.nynhp.org/freshwater-tidal-marsh/. Accessed March 23, 2023.