Physiognomy and Structure: Freshwater emergent marshes are dominated by medium to tall herbaceous plants, typically graminoids. Typical heights are 1-2 m, though a variety of low-forbs can predominate in some stands with heights rarely exceeding 0.5 m above the water surface. Vegetation cover is extremely variable from sparse to very dense. Shrubs are not common; when present, they tend to be on the drier portions of these communities.

Floristics: These freshwater marshes can be dominated by a variety of species. Typha spp. and Schoenoplectus spp. are common and widespread, but a wide variety of species may be dominant in any single stand. Dominants include Equisetum fluviatile, Eriocaulon aquaticum (in the eastern portion of the range and tends to be on more oligotrophic sites), Pontederia cordata (in the eastern portion of the range), Schoenoplectus acutus, Schoenoplectus americanus, Bolboschoenus fluviatilis (= Schoenoplectus fluviatilis), Schoenoplectus tabernaemontani, Sparganium spp., Typha angustifolia, Typha latifolia, Zizania aquatica, and Zizania palustris. Many other graminoids or broad-leaved forbs can be found in these marshes. Some of the common ones are Carex aquatilis, Carex lacustris, Carex pellita, Carex stricta, Eleocharis palustris, Leersia oryzoides, Peltandra virginica, and Sagittaria latifolia. Along the drier margins of some sites where soils are more saturated than flooded, Calla palustris, Symplocarpus foetidus, and Thelypteris palustris can sometimes be found, and in areas with more variable or shallow flooding, some wet meadow species may be present. Calamagrostis canadensis, Dulichium arundinaceum, and Spartina pectinata are typical of these areas. Floating-leaved or submergent species can be present where the water is deeper. Non-rooted floating-leaved species, typically Lemna spp., Spirodela polyrrhiza, and Wolffia spp., are often present to abundant in the spaces between the emergent plants. The invasives Lythrum salicaria and Phragmites australis are abundant in some sites and may even form nearly monotypic stands. Shrubs are absent to rare; when present, Alnus incana, Ilex verticillata, Myrica gale, and Spiraea alba are typical.

Dynamics:  Wave and current action is typically minor in these marshes. Especially strong storms may create especially strong waves and/or currents that break up marsh vegetation. Prolonged drought or a lowering of the water table may lead to exposure of the soil and invasion by plants more typical of wet meadows. Prolonged increases in the water level will favor submergent or floating-leaved vegetation. These dynamics of flood and drought are more common on the western edge of this group''s range, though not as common as in the Great Plains.