U.S. Army Corps of Engineers 2022
National Wetland Plant List, version 3.6
https://wetland-plants.sec.usace.army.mil/

If an earlier version of the NWPL is being cited, the proper information for each version of the NWPL is available on the NWPL website.

The nomenclature for the 2016 National Wetland Plant List (NWPL) can be cited as follows:

Lichvar, R.W., D.L. Banks, W.N. Kirchner, and N.C. Melvin. 2016. The National Wetland Plant List: 2016 wetland ratings. Phytoneuron 2016-30: 1–15.

You can access this through the NWPL website or http://www.phytoneuron.net/phytoneuron2016PUBS.htm

PLANTS is the preferred and recommended source. The NWPL was originally updated following BONAP nomenclature, but has since changed to PLANTS (hence both citations).

All the subspecies and varieties of a species in the same region have the same indicator status. The original 1988 National List of Plant Species that Occur in Wetlands included ratings for subspecific taxa. However, when this List was updated to the 2012 National Wetland Plant List (NWPL), all subspecies and varieties were given the indicator designation for the overall species.

The subregions and subregion ratings that were in place with the 2016 NWPL are still in place with the 2020 and 2022 NWPL, i.e., Quercus michauxii is FAC in the Atlantic and Gulf Coastal Plain’s Western Gulf Coastal Plain subregion and FACW throughout the rest of the region. Indicators can be different for a species between a region and its subregion and a change to one does not indicate a change for both.

The Alaska subregions and the subregion indicators from the 2016 NWPL are the same in the 2018 NWPL. Omission of the subregions was an oversight and the current NWPL contains the replaced subregions. Those subregions are still in place in both the 2020 and 2022 NWPL.

The lists of common plants by USACE District that are included on the NWPL web site are generated based on county-level occurrence data. Where we have a record of occurrence, a county is noted and those plant species occurring in the most counties within the District are considered most common. This method does not account for abundance, but does consider the most wide-spread species to be most common.

A plant species wetland indicator status is primarily based on estimated frequency of occurrence in wetlands vs. nonwetlands. There are over 8000 species on the NWPL and the majority do not have detailed frequency data. The process for development of the NWPL from its origins in the mid-1980s as the "National List of Plant Species that Occur in Wetlands," which was then under the auspices of the U.S. Fish and Wildlife Service, is documented in “Concepts and Procedures for Updating the National Wetland Plant List“ (http://wetland-plants.usace.army.mil/nwpl_static/data/DOC/NWPL/pubs/2008_Lichvar_Minkin.pdf). The process for how indicator status ratings are developed is documented in“Final Protocol for Assigning Wetland Indicator Status Ratings during National Wetland Plant List Update” (http://wetland-plants.usace.army.mil/nwpl_static/data/DOC/NWPL/pubs/2011v3_Lichvar_Gillrich.pdf ). Both of these documents, along with many others, including some frequency studies, are available on the NWPL website under NWPL Publications.

These abbreviations are the wetlands ratings and are also explained in the wetlands ratings section of the NWPL website (lower left of the homepage). They are: Indicator Status Abrv. Definitions - Short Version ( ERDC/CRREL TN-12-1 ) Obligate OBL Almost always occur in wetlands. Facultative Wetland FACW Usually occur in wetlands, but may occur in non-wetlands. Facultative FAC Occur in wetlands and nonwetlands. Facultative Upland FACU Usually occur in non-wetlands, but may occur in wetlands. Upland UPL Almost never occur in wetlands.

There is no formal definition for "true aquatic plants," but you can generate a region-specific list of aquatics and "floaters" from the NWPL using the Mapper tool. For wetland delineation purposes, all of the NWPL listed species (8000+) are rated OBL, FACW, FAC, FACU, or UPL, based on their estimated frequency of occurrence in wetlands. They are not rated on the hydroperiod or hydropattern (or “wetness”) of the wetlands that they inhabit. There is no formal definition for “true aquatic plants,” but they are described in the regional supplements where they are included as: “species that are normally submerged, have floating leaves or stems, require water for support, or desiccate in the absence of standing water.” However, many plants species generally considered aquatics (e.g., waterlilies Nymphaea and Nuphar) may grow in non-inundated areas. If you are interested in aquatic plants from an ecological perspective, the NWPL website has species listings by habitat (including aquatic) in the Biological Attributes section, in the Mapper on the right side of the NWPL homepage.

The NWPL only includes plant species that have been found to occur in wetlands somewhere within their range, and not those species that only occur in nonwetlands. Additionally, the NWPL only includes vascular plant species. Therefore, non-vascular plants, including bryophytes (mosses, such as Sphagnum spp.), are not included on the NWPL and do not have a wetland indicator status (either assigned or assumed). USDA’s PLANTS (https://plants.usda.gov/home), a complete listing of all plant species found within a given region, includes many UPL plants not found on the NWPL. It also includes non-vascular plants, such as bryophytes. This is why you may see bryophytes on some automated delineation data forms that use PLANTS. However, these bryophytes are still lacking a valid indicator status and cannot be assumed to meet any specific indicator status. A general caution with automated data forms: they are usually scored so that species not on the NWPL will be UPL. This works for many nonwetland species, but since no bryophytes are on the NWPL, any automated indicator status would be inaccurate for them. There should also be the usual cautions with assuming UPL for rare species, those with range expansions, nonnatives, etc., where they have not yet been evaluated for indicator status. While the NWPL does not include mosses, there have been other efforts to look at the wetland affinity of some mosses (see below). Seppelt, R.D., Laursen, G.A., Lichvar, R.W. 2008. A Guide to Alaskan Black Spruce Wetland Bryophytes. Species Specific to Delineation for Interior and South Central Regions. ERDC/CRREL TN-08-2. Vicksburg, MS: US Army Engineer Research and Development Center. https://erdc-library.erdc.dren.mil/jspui/bitstream/11681/2617/1/ERDC-CRREL-TN-08-2.pdf