The preserved and compressed remains of dead bog plants, usually either sphagnum moss or sedges. The natural acidity of some bogs prevents the dead plant material from decaying, so that it accumulates and over time forms thick deposits. Peat is extracted from these deposits and used for many purposes, including horticultural uses. It is termed moss peat (or peat moss) when derived mainly from sphagnum, or sedge peat when formed from sedges.