Accumulation of partially decayed vegetable matter, usually in a wetland environment.
Peat is an accumulation of partially decayed vegetable matter. This is invariably in a wet, low oxygen environment that allows the matter to accumulate but limiting decay due to the lack of oxygen. Example peat-forming locations include peat bogs, moors, muskeg, pocosins, mires, and peat swamps.
Geologically peat could be considered as being "on its way to becoming" lignite and eventually coal. In common with lignite and coal, it has a high carbon content, and after draining, can be burnt for fuel. However, it is a smoky fuel - more so than lignite. Some countries (e.g. Finland) class peat as a slowly renewing biomass fuel, although other sources class it as a fossil fuel.
Peat is also used in agriculture and horticulture as a growing medium. Peat can be mixed in with the soil to improve the soil's structure and improve its water and nutrient retaining abilities. It can also be used to increase soil acidity for plants which prefer an acidic soil.
Use this tag for all questions about using peat in a horticultural context.