Peat moss is derived from the decomposition in bogs of organic material, including mosses, reeds and shrubs. Peat bogs are found throughout the world but are principally located in the northern hemisphere. During the last ice age, melting glaciers left large bodies of water suitable for the formation of peat bogs. The natural accumulation of sedimentary deposits in these bodies of water was conducive to the growth of herbaceous organisms such as moss. As these organisms invaded the organic deposits, grew and died, they formed a bed of partially decomposed organic residue, commonly referred to as peat or peat moss. The types of peat in a peat bog depend upon the particular species of plant growing in the bog. Although there are several types of peat moss, sphagnum peat moss is the high quality peat moss preferred for horticultural purposes.