Swamps have 0,3-6 metres of peat. Peat is mainly formed from peat moss and other swamp plants. Because the swamp is wet, trees grow there poorly. There are many swamps in Finland because there is less evaporation than rain. Swamps form even on hillside terrain in Kuusamo. Nowadays the swamps that have few trees and are on a natural state are habitats that must be conserved according to the Forest Act.

• Pine mires are barren swamps, where stunted pine trees grow. Typical plants are peat moss and dwarf shrubs, like marsh Labrador tea, bog whortleberry, dwarf birch and cranberry.
• Hardwood swamps are nutritious wooded swamps that are dominated by spruce trees. Typical plants are haircap, wood horsetail, bog whortleberry, carex and cloudberry.
• Bogs are treeless and wet open swamps, where birds live abundantly
• Fens are lush open swamps, where junipers, tormentils and the protected lady's slipper orchid grow.
• Ways how swamps can form: 1. A lake grows shut, 2. A forested area becomes a swamp in dells. 3. Ground rising from the sea becomes a swamp.