Peat Moss: What It Is and How to Use It

Achieve the Right Balance Between Drainage and Water Retention

Closeup of peat moss

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Peat moss is recommended often in gardening tutorials. Though the dark-brown fibrous material can be useful for growing plants, there's much debate about its environmental safety. Find out more about peat moss, what it is, how it compares to other materials, how it's used, its benefits, and its potential downsides.

What Is Peat Moss?

Peat moss is a soil amendment that is harvested from peat bogs. Many of these bogs are found in wetland areas of Canada. Peat bogs are formed, over the course of very long periods of time, as organic materials partially decompose. Because of the water in these bogs, anaerobic conditions are maintained, conditions that retard full decomposition. The result is that the peat moss is preserved almost indefinitely.

Although sometimes referred to as "peat" for short, peat moss and peat are not, technically, the same thing. "Peat" is the broader term: Peat moss is just one of the products harvested from peat bogs. Other kinds of peat come from the partial decomposition of other organic materials. The "moss" in "peat moss" refers specifically to sphagnum moss (for example, Sphagnum cymbifolium).

Peat moss is commonly sold in bales (covered in plastic) at home improvement centers. When you break open a bag, the substance that you will find inside resembles a very dry, caked-up soil.

How Peat Moss Is Different from Sphagnum Moss

"Peat moss" and "sphagnum moss" are closely related, but the two terms are not synonymous. Here is how the two differ:

First of all, "sphagnum moss" can refer to a living plant. There are 120 species of this type of moss plant. Sphagnum moss is native to many countries across the globe, but it is especially prevalent in the Northern Hemisphere. "Peat moss," by contrast, does not refer to something living; it refers to something long dead.

Like peat moss, sphagnum moss is harvested for the horticultural trade. For example, it is commonly used to line wire baskets for hanging plants, to retain the soil. But the sphagnum moss used for this purpose was a plant growing in nature not that long ago. You can also tell from its appearance that it is a type of moss, whereas peat moss bears more of a resemblance to soil.

How Peat Moss Is Used

Sphagnum peat moss is widely used in soilless potting mixes. So if you have started plants indoors from seed, then you have very likely already dealt with peat moss. A soilless potting mix is much better to use for starting seeds than regular soil, for the following reasons:

  • Regular soil is too heavy for plants just sprouting from seed. The tender, young roots have trouble pushing through it.
  • Drainage is also generally poorer in regular soil, and seeds may rot in it before they ever get a chance to sprout.
  • Regular soil can also harbor pathogens that could easily kill the young plants.

But peat moss has other uses, as well. Outdoors, it can be tilled into a planting bed where the soil is not sufficiently friable. Peat moss will lighten up the soil in your garden, which may have become compacted over the years, resulting in inadequate drainage.

But you do not want all of the water to pass quickly through your soil. An ideal soil will retain enough moisture to keep your plants irrigated. It is a delicate balance, and peat moss, with its ability to also retain water, will help you achieve that balance.

Why Peat Moss Is an Effective Soil Amendment

The popularity of peat moss as a soil amendment can be accounted for by listing the following pros:

  • Inexpensive
  • Lightweight (which helps you as well as your plants, because pots filled with such soilless mixes are easier to transport)
  • Promotes sufficient drainage
  • Retains just the right amount of water
  • Sold to the public after being sterilized to remove pathogens

What Are the Drawbacks of Peat Moss

Peat moss does, however, come with some cons, as well:

  • It doesn't add any nutrients to the soil.
  • Nor is it considered sustainable. It takes hundreds of years for peat moss to be created in nature. That is why, increasingly, coir is being used as an alternative to peat moss in soilless potting mixes. Coir is a by-product of coconut fiber and is, therefore, renewable.
  • Peat moss is acidic. So while it is an ideal soil amendment for acid-loving plants, you may have to add garden lime to your planting bed to raise its soil pH over time if you are growing plants there that want a higher pH.