Marshes are wetlands that are periodically inundated by standing or slowly moving water and hence are rich in nutrients. Marshes are mainly wet, mineral-soil areas, but shallow, well-decomposed peat may be present. They are characterized by an emergent vegetation of reeds, rushes or sedges and the absence of woody vegetation.
Swamps are wetlands where standing or gently moving waters occur seasonally or persist for long periods, leaving the subsurface continuously waterlogged. The vegetation may consist of dense coniferous or deciduous forest, or tall shrub thickets.
Bogs are peat-covered wetlands (peatlands), in which the vegetation shows the effects of a high water table and a general lack of nutrients. The plant community is dominated by cushion-forming Sphagnum mosses (peat mosses), ericaceous shrubs and black spruce trees.
Fens are peatlands characterized by a high water table, but with very slow internal drainage by seepage. Similar to bogs, the surface water in fens is also generally nutrient poor. Dominant plants include black spruce, tamarack, sedges, grasses, and various mosses.