Harvested primarily in Canada and North America, sphagnum peat moss (Sphagnum andersonianum) is an all-purpose soil amendment that can also be used alone in certain horticultural operations. The peat moss sold in garden centers is the partially decayed remains of plants grown in high-acid peat bogs. The high-acid content of the water slows down or halts the decay process, resulting in a tough, stringy, fibrous product for use in your garden.
Plants grown in containers require a light, aerated soil mixture capable of retaining a lot of water. Adding sphagnum moss to the soil of potted plants does the trick. Its stringy, fibrous texture creates air pockets in the soil; it can hold up to 20 times its weight in water.
Improves Garden Soil
When added to garden beds, sphagnum moss will create a more desirable growing medium whether your garden soil is clay or sand. Peat moss loosens up heavy clay soils, creating air pockets between the tightly packed microscopic clay soil particles, helping it to drain more rapidly and keeping the plants' roots from becoming waterlogged. At the same time, it increases the soil's ability to retain moisture and nutrients, which tend to drain away too rapidly in sandy soils.
Because it contains specific fungistatic substances, sphagnum moss is widely used for indoor seed starting, according to Texas A&M University Extension. The fungistatic substances in sphagnum moss inhibit the development of a fungal disease called "damping off," which is always fatal to small seedlings. It is thought to be present in most soils and is nurtured by the warm, moist environment conducive to seedlings' germination and early growth. It most often strikes seedlings approximately 7 to 10 days after germination and emergence.