There is a lot of confusion about the labeling of sphagnum moss and peat moss. The important difference between these two mosses has never been clearly explained to most gardeners. So, this article will try to clear up the confusion and describe how they are both similar, yet two very different soil amendments.
Sphagnum moss is pH neutral.
Yes, you read that right. Generally, the pH of sphagnum moss is pH neutral. It is soft, pliable, and very water-retentive. It is used to line baskets, as a seed-starter medium, as a medium that most big-box store Phalaenopsis orchids are growing in, and as an amendment in potting soils. Good quality sphagnum moss will be pure moss, without any other plant material incorporated.
Sphagnum moss and peat moss begin life the same way, from the same plant. Sphagnum moss grows on the surface of the soil, generally where the climate is mild, humid, gets plenty of rain, and perhaps somewhat shaded. Sphagnum moss grows in abundance in parts of Canada, Peru, New Zealand, Ireland, and Scotland. It grows all over the world, but these areas are where most of our commercially available moss comes from. Sphagnum moss is a living plant when harvested, but when we purchase it, it has been thoroughly dried. Basically, there are two forms of the sphagnum moss when sold commercially, long-fibered moss and milled moss. They are the same moss, but the long-fibered is left in its natural form and the milled is moss that has been finely chopped.
Peat moss is very acidic and is high in tannins.
Now Peat moss is quite different, and to add confusion, it is often labeled as sphagnum peat moss. It begins its life as sphagnum moss, but over time the sphagnum moss dies and is over-grown by new sphagnum moss. This is repeated over and over, and after hundreds or even thousands of years these many layers of dead sphagnum moss form a bog. This layer of dead, compacted moss is now called peat moss. Peat moss is saturated with water. Water is a necessary element for a bog to form. Peat moss is not pure moss and is a mixture of many plant varieties that died along with the moss and can have twigs and dead insects. Whereas sphagnum moss has a neutral pH, peat moss is very acidic and is high in tannins. Peat moss is sold in compressed bales and, like milled sphagnum moss, it is used in potting and garden soils. Peat moss is a less expensive amendment in potting and garden soils, and it is a great medium for growing acid-loving plants.
Practically everyone who grows plants, uses some sort of sphagnum moss. It is found in most commercially available seedling mixes, potting soils, garden soils, in bales labeled as Sphagnum Peat Moss, in 2 cf. bags labeled Milled Sphagnum Moss, in moss-lined baskets, and in small bags labeled Long-fibered Sphagnum Moss. This is good information for pepper and tomato growers who make their own seedling mixes. The sphagnum moss is great component for water retention and will not lower the pH of your mixes.