Sphagnum is a
genus of between 151-350
species of
mosses commonly called
peat moss, due to its prevalence in
peat bogs and mires. A distinction is made between sphagnum moss, the live moss growing on top of a peat bog, and sphagnum peat moss, the decaying matter underneath.
[1] Bogs are dependent on precipitation as their main source of food and nutrients, thus making them a favourable habitat for sphagnum as it can retain water and air quite well. Members of this genus can hold large quantities of water inside their cells; some species can hold up to 20 times their dry weight in water, which is why peat moss is commonly sold as a
soil amendment. The empty cells help retain water in drier conditions. In wetter conditions, the spaces contain air and help the moss float for photosynthetic purposes. Sphagnum and the peat formed from it do not decay readily because of the
phenolic compounds embedded in the moss's cell walls. An additional reason is that the bogs in which Sphagnum grows are submerged, deoxygenated, and favor slower anaerobic decay rather than aerobic microbial action. Peat moss can also
acidify its surroundings by taking up
cations such as
calcium and
magnesium and releasing
hydrogen ions.