What Is Peat Moss? Pros and Cons of Using Peat Moss

Peat moss is decomposed organic matter that occurs naturally in cold, marshy ecosystems. Most peat moss sold in the northern hemisphere is harvested from the chilly peatlands of Canada and the northern United States.

Peat moss is not a plant species but rather an amalgamation of fibrous material salvaged from cold weather wetlands. The most common plant material in peat moss is sphagnum moss. As such, some peat moss gets marketed in stores as sphagnum peat moss.

As a growing medium and soil amendment, peat moss offers numerous advantages to home gardeners and professional farmers.

1. 1. Great for plants that need acidic soil: Gardeners often use peat moss to manage soil pH. When planting species that thrive in acidic soil—such as blueberries or azaleas—mix peat moss into your potting soil to achieve an acidic pH. Peat moss can also help neutralize alkaline soil by bringing down the overall pH. This can help you grow plants that like roughly neutral soil like camellias.
2. 2. Excellent water-holding capacity: Peat moss is known for its remarkable water retention. Some gardeners mix it into sandy soil to keep it from draining too quickly.
3. 3. Disease-resistant: Peat moss is sterile. This means it doesn't arrive ridden with microorganisms, pathogens, and weed seeds. This sterility makes peat moss an excellent growing medium for young plant roots that might be susceptible to disease or parasites. Many growers specifically use it for seed starting.
4. 4. Works for hydroponic gardening: Some gardeners favor soilless hydroponic gardening, for which peat moss is an excellent growing medium that plant roots can cling to.
5. 5. Mixes well in potting soil: Peat moss blends right into a soil mix alongside coconut coir (coco coir), perlite, and vermiculite. The moss holds water while the other materials help with aeration.
6. 6. Won't compact: Unlike traditional soil, peat moss does not compact when people walk on it. Peat moss fits nicely into topsoil where it retains its spongy nature. It also works as a soil conditioner for dense clay soil that compacts so densely it can suffocate plant roots.

Despite peat moss's many uses in the garden, it comes with downsides.

1. 1. Environmental concerns: Peat moss is effectively a non-renewable resource because it takes many thousands of years to form. The peat moss you see in garden centers comes from Canadian (and sometimes American) bogs. Once it is extracted, it is gone for millennia. The harvesting of peat moss also releases carbon dioxide into the air and even clears the way for methane release. Methane and CO2 are both greenhouse gasses known to contribute to global warming.
2. 2. Expensive: Peat moss costs much more per square foot than traditional soil. More affordable—and more environmentally friendly—alternatives include coconut coir (coco coir) and compost from your own household vegetable waste. Even traditional mulch can do the trick when you want to trap moisture in the soil on hot days.
3. 3. Not ideal for certain plants: Some plants do best in alkaline soils. This includes lavender, ginger, daylilies, blackberries, and raspberries. These plants should not be planted with peat moss.
4. 4. Cracks soil: When peat moss dries out, it can make the surface of your soil crack.

The core difference between peat moss and sphagnum moss is that sphagnum moss is typically sold as a living plant, whereas peat moss is a mixture of decayed organic materials found in cold water bogs. The decomposition process occurs at the bottom of the bog over thousands of years. In most cases, decayed sphagnum moss comprises the primary material in peat moss. While peat moss resembles soil, you’ll likely find bright green sphagnum moss lining the top layer of potted houseplants.

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