There are three types of wetlands based on the most common vegetation. Each wetland type may have plants of the other two.

Swamps: A wetland in which over half the plants are trees and contains standing water most of the year. Commonly, swamps contain lakes, some so acidic they are barren of fish. Swamps are the primary producer of the peat that becomes coal. The water may be ten feet deep.

Marshes: These are wetlands of grasses, reeds, rushes, and cattails. Water level varies from just covering the ground to a few feet deep. They commonly occur as coastal salt and brackish marshes and as Prairie Potholes on the glacial moraines of North and South Dakota, and Minnesota. Because they are shallow, well oxygenated and often involved in tidal action, they seldom if ever, collect enough peat to form coals.

Bogs: The primary vegetation is moss, commonly sphagnum (common to gardeners). Bogs form much of the tundra of the northern latitudes. They are usually very acidic and form many of the current peat cutting areas including those of Canada and Scotland. Most bog peat coals are low quality and thin.