Pocosins occur in the Atlantic Coastal Plain of North America, occupying poorly drained higher ground between streams and floodplains. Seeps cause the inundation. There are often perched water tables underlying pocosins.
A distinction is sometimes made between short pocosins, which have shorter trees, deeper peat, and less soil nurtients, and tall pocosins, which have taller trees, shallow peat, and more soil nutrient. Where soil saturation is less frequent and peat depths shallower, pocosins transition into pine flatwoods. A loose definition of "pocosin" can include all shrub and forest bogs, as well as stands of Atlantic White Cypress and Loblolly Pine on the Atlantic Coastal Plain. A stricter definition restricts pocosins to shruby "short pocosins" and Pond Pine-forested "tall pocosins".
Pocosin ecosystems are fire-adapted (pyrophytic). Pond Pines exhibit serotiny, such that wildfire can create a pond pine seedbed in the soil. Wildfires in pocosins tend to be intense, sometimes burning deep into the peat, resulting in small lakes and ponds.
Wildfires occurring about once a decade tend to cause pond pine trees to dominate over other trees, and cane (Arundinaria) rather than shrubs to dominate the understory. More frequent fires result in a pyrophytic shrub understory. Annual fires prevent shrub growth and thin the Pond Pine forest cover, creating a flooded savanna with grass, sedge, and herb groundcover.
The word pocosin is thought to come from an Eastern Algonquian language word.