The marsh community overlaps somewhat with the wet meadow, but includes species that prefer standing water for prolonged periods throughout the growing season.  Woody vegetation accounts for less than 30% of the areal cover.

Marsh vegetation consists of a variety of herbaceous species,  with cattails representing one of the most common plants. The presence of standing water throughout the growing season contributes to an extremely high level of productivity. Hundreds of species of fish, birds, and other wildlife spend all or part of their lives in marshes. Marshes were once common throughout Illinois, but today, only a few remnants remain.  Many of these areas are part of larger wetland complexes, occurring along the border of a pond or within the floodplain of a stream.

The soils in this community consist of silty, loamy, and clayey materials. Some organic soils are included. The reaction is typically neutral. The major soils include ponded phases of Karnak clay, Comfrey loam, Palms muck, Adrian muck, and Darwin silty clay.

*Used throughout the community descriptions to indicate the most commonly occurring code in Illinois