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Macrogroup Detail Report: M303
Juncus effusus - Lythrum salicaria - Phalaris arundinacea Eastern North American Ruderal Marsh, Wet Meadow & Shrubland Macrogroup

The U.S. National
Vegetation Classification
This macrogroup includes disturbed herbaceous or shrub marshes and wet meadows in the eastern and southeastern United States and southeastern Canada, which are dominated by native ruderal or exotic species.
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Translated Name:Common Rush - Purple Loosestrife - Reed Canarygrass Eastern North American Ruderal Marsh, Wet Meadow & Shrubland Macrogroup
Colloquial Name:Eastern-Southeastern North American Ruderal Marsh, Wet Meadow & Shrubland
This macrogroup includes disturbed marshes and wet meadows in the eastern and southeastern United States and southeastern Canada, which are dominated by native ruderal or exotic species. This macrogroup is composed of herbaceous- or shrub-dominated, temporarily, irregularly, seasonally or semipermanently flooded wetlands. Sites often have a history of significant disturbance such as heavy pasturing, agricultural or urban stormwater runoff, or alteration in hydrologic regimes. Along with the wide range in flooding regimes, there can be a wide variety of dominant species, some of which can form near monocultures. Some common herbaceous dominants include Juncus effusus, Lythrum salicaria, Phalaris arundinacea, exotic Phragmites australis (chloroplast haplotype M), Polygonum cuspidatum, Scirpus cyperinus, and Typha spp. Typical shrubs include Ligustrum sinense, Lonicera maackii, and in southern coastal areas Tamarix spp.
These are herbaceous or shrub wetlands that are characterized by ruderal conditions or dominance by exotic plant species. Examples would include wetlands dominated by exotic graminoids, such as Arthraxon hispidus, Arundo donax, Microstegium vimineum, Pennisetum purpureum, Phalaris arundinacea, and exotic Phragmites australis (chloroplast haplotype M) (Saltonstall 2002). Also included here are herbaceous or shrub wetlands which may have been artificially impounded or severely disturbed by vehicles or equipment, and are vegetated with exotic or ruderal native plants. The key distinction between this macrogroup and other herbaceous wetlands in the same region is the dominance by ruderal or exotic species and very often a significant disturbance to the natural ecological dynamics of the site.
These herbaceous wetlands are characterized by ruderal conditions or dominance by exotic plant species.
Synonomy: >< Gulf Coast Fresh Marsh SRM 807 (Shiflet 1994)
> Palustrine Emergent Wetlands (Cowardin et al. 1979)

Related Type Name:The natural vegetation macrogroups (M067, M069, and M071) which correspond to this alliance (M303) are split into very broad areas of the eastern and central United States.

Short Citation:
  • Cowardin et al. 1979
  • Faber-Langendoen et al. 2017a
  • Saltonstall 2002
  • Shiflet 1994
States/Provinces:AL, AR, CT, DE, FL, GA, IA, IL, IN, KY, LA, MA, MD, ME, MI, MN, MO, MS, NB, NC, NH, NJ, NS, NY, OH, ON, PA, PE, QC, RI, SC, TN, TX, VA, VT, WI, WV
Nations:CA, MX, US
Range:This macrogroup is widespread across the eastern and southeastern United States and southeastern Canada.
US Forest Service Ecoregions
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These are herbaceous wetlands that are characterized by graminoid or forb vegetation but are variable in physiognomy. The vegetation can include shrubs as well. Sites can have relatively sparse and low (0.5 m) to very dense and tall (2-3 m) vegetation.
This macrogroup can have a wide variety of dominant and associated herbaceous forb, graminoid, or shrub species depending on geography, disturbance history, local seed sources, hydrology, and other factors. Andropogon glomeratus, Calamagrostis canadensis, Juncus effusus, Leersia oryzoides, Scirpus cyperinus, Typha angustifolia, and Typha latifolia are typical native graminoid species which are found in ruderal wet meadows and marshes. This macrogroup also includes wetlands dominated by the exotic grasses Arthraxon hispidus, Arundo donax, Microstegium vimineum, Pennisetum purpureum, Phalaris arundinacea, and exotic Phragmites australis (chloroplast haplotype M) (Saltonstall 2002). In the cool-temperate climatic zone, other species commonly present to abundant include Butomus umbellatus, Hesperis matronalis, Iris pseudacorus, Lythrum salicaria, Lysimachia nummularia, Myosotis scorpioides, and Polygonum cuspidatum. Exotic shrub-dominated wetland vegetation is also included here, such as vegetation dominated by Ligustrum sinense, Lonicera maackii, and Tamarix spp. This does not include tall shrubs such as Triadica sebifera. Also, there is ruderal vegetation dominated by annual plants in open-canopy flood zones which are exposed and even dry during the summer. This includes drawdown zones of reservoirs and other wetland habitats.
Examples of this macrogroup occur in temperate zone wetlands in basins, along lakeshores, pondshores, in floodplains or on depositional bars along rivers or streams. These sites can have natural or altered flooding regimes, including the edges of impoundments. They are flooded for at least some portion of the growing season, such as temporarily, irregularly (inundated only during spring and storm tides), seasonally or semi-permanently flooded (Cowardin et al. 1979). Flooding can range from short, shallow flooding that dries out during the growing season to semi-permanent flooding where surface water is present year-round most years. Generally the vegetation is on hydric soils, except for temporarily flooded sites and impounded sites. Sites have often been disturbed, either from natural processes, such as flooding, or anthropogenic actions. Due to their aggressive nature, some of the dominant plant species in this macrogroup do not require disturbance before invading an area, though perhaps spreading from disturbed areas adjacent to the site.
These wetlands are subject to natural disturbances, such as flooding or hurricanes in coastal areas. Hydrologic variation, such as increased flooding or drying, can have a great impact on these sites. The variation may be the result of natural causes or caused by human activities. Many sites have been subjected to anthropogenic disturbance or are dominated by invasive exotic plants.
C. Nordman and C. Lea      Version Date: 05Jun2015

  • Cowardin, L. M., V. Carter, F. C. Golet, and E. T. LaRoe. 1979. Classification of wetlands and deepwater habitats of the United States. FWS/OBS-79/31. USDI Fish & Wildlife Service, Office of Biological Services, Washington, DC. 103 pp.
  • Faber-Langendoen, D., J. Drake, S. Gawler, M. Hall, C. Josse, G. Kittel, S. Menard, C. Nordman, M. Pyne, M. Reid, L. Sneddon, K. Schulz, J. Teague, M. Russo, K. Snow, and P. Comer, editors. 2010-2017a. Divisions, Macrogroups and Groups for the Revised U.S. National Vegetation Classification. NatureServe, Arlington, VA. plus appendices. [in preparation]
  • Saltonstall, K. 2002. Cryptic invasion by a non-native genotype of the common reed, Phragmites australis, into North America. Proceedings of the National Academy of Science 99:2445-2449.
  • Shiflet, T. N., editor. 1994. Rangeland cover types of the United States. Society for Range Management. Denver, CO. 152 pp.

USNVC Credits: Detailed Description of the National Vegetation Classification Types

Date Accessed:

To cite a description:
Author(s). publicationYear. Description Title [last revised revisionDate]. United States National Vegetation Classification. Federal Geographic Data Committee, Washington, D.C.

About spatial standards:
The United States Federal Geographic Data Committee (hereafter called the FGDC) is tasked to develop geospatial data standards that will enable sharing of spatial data among producers and users and support the growing National Spatial Data Infrastructure (NSDI), acting under the Office of Management Budget (OMB) Circular A-16 (OMB 1990, 2000) and Executive Order #12906 (Clinton 1994) as amended by Executive Order #13286 (Bush 2003). FGDC subcommittees and working groups, in consultation and cooperation with state, local, tribal, private, academic, and international communities, develop standards for the content, quality, and transferability of geospatial data. FGDC standards are developed through a structured process, integrated with one another to the extent possible, supportable by the current vendor community (but are independent of specific technologies), and publicly available.

About this document
This document contains type descriptions at the Macrogroup level of the U.S. National Vegetation Classification. These descriptions were primarily written by NatureServe ecologists in collaboration with Federal Geographic Data Committee Vegetation Subcommittee and a wide variety of state, federal and private partners as a part of the implementation of the National Vegetation Classification. Formation descriptions were written by the Hierarchy Revisions Working Group. The descriptions are based on consultation with natural resource professionals, published literature, and other vegetation classification systems. The Ecological Society of America's Panel on Vegetation Classification is responsible for managing the review and formal adoption of these types into the National Vegetation Classification. Partners involved in the implementation of the USNVC include:

U.S. Government
  • Department of Agriculture (USDA)
  • Department of Commerce (DOC)
  • Department of Defense (DOD)
  • Department of the Interior (USDI)
  • Forest Service (FS) - Chair
  • National Agriculture Statistical Service (NASS)
  • Natural Resources Conservation Service (NRCS)
  • National Oceanic and Atmospheric Administration (NOAA)
  • National Marine Fisheries Service (NMFS)
  • U.S. Army Corps of Engineers (USACE)
  • U.S. Navy (NAVY)
  • Bureau of Land Management (BLM)
  • Fish and Wildlife Service (FWS)
  • National Park Service (NPS)
  • U.S. Geological Survey (USGS)
  • Environmental Protection Agency (EPA)
  • National Aeronautics and Space Administration (NASA)
Non U.S. Government
  • NatureServe (NS)
  • Ecological Society of America (ESA)

Given the dynamic nature of the standard, it is possible a type description is incomplete or in revision at the time of download; therefore, users of the data should track the date of access and read the revisions section of the website to understand the current status of the classification. While USNVC data have undergone substantial review prior to posting, it is possible that some errors or inaccuracies have remained undetected.

For information on the process used to develop these descriptions see:

Faber-Langendoen, D., T. Keeler-Wolf, D. Meidinger, D. Tart, B. Hoagland, C. Josse, G. Navarro, S. Ponomarenko, J.-P. Saucier, A. Weakley, P. Comer. 2014. EcoVeg: A new approach to vegetation description and classification. Ecological Monographs 84:533-561 (erratum 85:473).

Franklin, S., D. Faber-Langendoen, M. Jennings, T. Keeler-Wolf, O. Loucks, A. McKerrow, R.K. Peet, and D. Roberts. 2012. Building the United States National Vegetation Classification. Annali di Botanica 2: 1-9.

Jennings, M. D., D. Faber-Langendoen, O. L. Louckes, R. K. Peet, and D. Roberts. 2009. Standards for associations and alliances of the U.S. National Vegetation Classification. Ecological Monographs 79(2):173-199.

FGDC [Federal Geographic Data Committee]. 2008. Vegetation Classification Standard, FGDC-STD-005, Version 2. Washington, DC., USA. []

For additional information contact:

  • Implementation of the U.S. National Vegetation Classification Standard - Alexa McKerrow (
  • NatureServe's Development of NVC Type Descriptions - Don Faber-Langendoen (don_faber-
  • Ecological Society of America's Review of the Type Descriptions
  • Federal Geographic Data Committee - Vegetation Subcommittee's Activities - Marianne Burke (
Jim Drake of NatureServe made many contributions to our understanding of this marsh vegetation.