The terms “sphagnum moss” and “peat moss” are often used interchangeably, causing confusion among consumers. Both materials originate from the Sphagnum plant genus, but their biological states and properties differ significantly. Sphagnum moss is the living or recently dried plant material, while peat moss is the highly decomposed, ancient accumulation of that material. Understanding this difference is key to selecting the correct product for specific horticultural needs.
Defining the Relationship: Live Sphagnum vs. Decayed Peat
Sphagnum is a genus of hundreds of moss species that form dense mats on the surface of wetlands known as bogs. The living moss, or the recently dried form sold commercially, is characterized by long, intact, stringy fibers. It ranges from pale green to light tan when dried, maintaining a soft, pliable texture.
Peat moss is the dark, dense, and highly decomposed organic layer found beneath the living moss. This material is dead plant matter accumulated over centuries. Decomposition breaks down the original structure, resulting in a fine, crumbly, dark brown texture.
The distinction is based on the degree of decay and depth of harvest. Living moss is collected from the surface, while peat moss is harvested from buried layers. This difference in composition results in drastically different chemical properties, particularly acidity.
The Formation and Harvesting Process
The formation of peat moss is driven by unique environmental conditions. Peatlands are waterlogged, acidic environments naturally low in oxygen, creating anaerobic conditions. This environment inhibits the microbial action that normally causes organic material to decay quickly.
This slow, incomplete decomposition allows dead moss to accumulate beneath the active surface layer. Peat forms extremely slowly, often only 0.5 to 1 millimeter per year. The deep deposits used in gardening took thousands of years to create.
Acquisition methods reflect this difference in formation time. Live or dried Sphagnum moss is harvested from the surface of active bogs. When managed carefully, this surface layer can regenerate within a few years, making it a potentially renewable resource.
In contrast, peat moss is extracted through a process resembling mining. The bog surface is cleared, and the underlying peat is drained and dried. Large vacuum harvesters remove the dried material, removing a resource that cannot be replaced within a human lifespan.
Comparing Practical Uses and Horticultural Properties
The physical structure and chemical composition of each material determine its best use in horticulture. Sphagnum moss is valued for its unique cellular structure, allowing it to absorb and hold an exceptional amount of water, often up to 20 times its dry weight. This characteristic makes the long-fibered moss an excellent choice for lining hanging baskets, air layering, and creating moss poles.
The moss is also favored as a growing medium for specialized plants, such as orchids and carnivorous species. This is due to its relatively neutral pH and its ability to provide moisture without waterlogging roots. Its fibrous structure provides excellent aeration and a clean medium for propagating cuttings.
Peat moss, being highly decomposed, has a much finer, less structured texture than its living counterpart. It is primarily used as a soil amendment or a main component in potting mixes rather than as a standalone medium. The fine particles help improve the structure of both sandy and clay soils by increasing water retention and promoting better aeration.
A significant property of peat moss is its high acidity, typically registering a pH between 3.0 and 4.5. This low pH makes it suitable for cultivating acid-loving plants. Gardeners incorporate peat moss into mixes to help maintain the low pH required by plants such as azaleas, rhododendrons, and blueberries.