The class Phragmito-Magno-Caricetea includes marshes, i.e. species-poor vegetation of large perennial grasses, tall sedges, and in some cases also of broad-leaved herbs, which occurs in shallow, fresh-water or brackish wetlands. Due to their dense system of roots and rhizomes these plants can be firmly rooted even in unstable, muddy, and often flooded substrates, and are capable of spreading vegetatively. Most stands of these vegetation types are dominated by a single, often tall species, which produces large amounts of biomass, and significantly contributes to terrestrialization. Large grasses are most typical of habitats with mineral soil and deeper water, while tall sedges spread in later stages of terrestrialization, when the bottom is covered by a layer of organic sediment, and the water becomes shallower. Vegetation of this class occurs mainly in the littoral zones of still water bodies, but specific types also occur on stream banks. Phragmito-Magno-Caricetea is widespread in the temperate zone of Eurasia and North America, but it also occurs in either cooler or warmer zones, and on other continents.