Peat moss and sphagnum moss are products from a class of bryophytes (mosses) called Sphagnopsida. Peat moss refers to the product gardeners purchase in bales or large bags for use as a soil amendment. Sphagnum moss is used primarily in crafts and packing. While peat moss and sphagnum moss come from the same plant, they represent different points in its life cycle.
Sphagnum moss grows in peatland bogs, a type of wetland with very little water flow. The cool climate and acidic, low-nutrient nature of the stagnant water are ideal conditions for the growth of Sphagnum moss. Sphagnum moss plants live on the water's surface, collecting along the edges of the bog and spreading outward. As the floating plants die, the dead and decaying material forms a mat beneath the living plants. This mat is referred to as "peat." New moss plants continue to grow on top of the peat, continuing the cycle. In the United States there are 51 million acres of peat, distributed across 42 states. Some of the peatlands are thousands of years old.
The mat of decaying and dead plant matter, which is harvested and dried, is referred to as "peat," but also "peat moss" or "sphagnum peat moss." It has antiseptic properties and was used for dressing wounds in World War I. The Eskimos have used it to treat diaper rash. In Ireland, dried peat is burnt as a fuel to heat homes. In the U.S. today, peat moss is employed as a soil additive and potting medium. It can absorb up to 20 times its weight in water, and conditions the soil by adding air and allowing moisture to penetrate. With a pH of 4.0, sphagnum peat moss is useful for plants such as azaleas and blueberries that like acidic soil. Peat is also used to manufacture the peat pots used for growing seedlings.
The living plant that grows on top of the peat bog is dried and sold as "sphagnum moss." It is used in the craft and garden industries to line baskets and as a packing material in shipping bare-root plants. Sphagnum moss has been implicated a fungal disease called Sporothrix schenckii, which occurs when moss infected with the fungus comes in contact with an opening in the skin. Gardeners and others who work with sphagnum moss need to wear gloves and long sleeves when handling the product. Sphagnum peat moss, which is composed of dead and decaying matter, has not been found to harbour the fungus.
Controversy surrounds the harvesting of sphagnum peat moss, centring on whether or not it is a renewable resource. Industry representatives point out that peat forms constantly in the bogs and is, therefore, renewable. Horticulturist Linda Chalker-Scott argues, however, that peat moss can't be considered a renewable resource because the process of harvesting changes the bog in such a way that natural regeneration is not possible.