The Problem with Using Peat Moss (and What to Use Instead)

Almost any potted plant you can buy grows in a soil mix containing peat moss, and most bagged potting soil does. You can also buy it to mix into your potting soil blend. It's especially useful for growing flowers and food in containers because it helps plants maintain the moisture they need. Even though this brown, fibrous substance is so common and helpful in the gardening world, peat moss has long been a sore point for those in the industry due to its sustainability—or, more accurately, the lack thereof. Here's what you need to know about the downsides of peat moss and what you can use instead.

What Is Peat Moss?

When discussing peat moss for gardening, at least in the United States, that means sphagnum moss. Sphagnum is a type of moss most notable for its fantastic absorption ability. It can take in 20 times as much water by weight as its dry weight, so it's essentially a natural sponge. Sphagnum moss prefers growing in moist tundra-type areas, and most of what gets used for gardening in the United States comes from peat bogs in northern Canada. As the sphagnum moss dies in these bogs, it slowly decays into the peat moss that's so popular for gardening.

What Is It Used For?

Potting mix used for container gardening has to be able to drain well to avoid root rot, but also has to hold enough water for the plants to have a chance. As a solution to this challenge, "peat moss is a marvelous substance," says Linda Chalker-Scott, a horticulture expert. She points out that it helps with both of these needs, acting like tiny sponges throughout the soil that hold the water and slowly release it as a plant's roots need it.

Why Should You Care About Peat Moss?

That's a tricky question. The answer has to do with what happens when it's harvested. Remember, peat forms very slowly in cool wetlands as sphagnum moss decays. The bogs are called "carbon sinks" due to the massive amounts of carbon they store—far more than trees. When peat moss is harvested, carbon dioxide is released, and carbon dioxide is a significant contributor to climate change. While some scientists view peat bogs as a possible aid in reversing climate change, the very increases in heat and drought brought about by climate change may destroy the bogs.

The industry says it harvests less than 2% of the existing supply each year and that this reasonably low collection amount keeps up with demand. But even though that doesn't sound like a lot, harvested areas can't recover quickly enough for peat to be considered a renewable resource.

"We cannot replace the peat biomass that we remove from a bog in a human being's lifetime," says Paul Short, the president of the Canadian Sphagnum Peat Moss Association. However, he points out that the CSPMA engages in aggressive restoration efforts, including reseeding from nearby bogs to reenter the sphagnum-to-peat process.

Despite these restoration efforts, peat probably can't be harvested again for a thousand years or more, at least not in the same quantities from the same bog. "It's almost impossible to get it back to the way it was," says Chalker-Scott. "I compare it to cutting down old-growth forests. Sure, you can plant new trees, but it will take a long time."

Since peat bogs are the single largest carbon sink on the planet, they're one of the ways nature helps minimize the greenhouse effect of too much of this gas in the atmosphere. When you remove the peat moss, not only does it release carbon dioxide, but it's that much less carbon getting stored.

What Are the Alternatives to Peat Moss?

Chalker-Scott recommends avoiding it altogether. "It doesn't do anything that's crucial for plant life," she says. "Otherwise, there wouldn't be any plants except right around peat bogs." Peat moss makes soil better able to absorb and hold water, but it isn't required. Given how slowly peat moss forms in nature, collecting it is complex to do in a genuinely sustainable way—and if you don't need it, why use it at all?

Luckily, plenty of other options exist. When it comes to bagged potting mixes, you can find ones that don't use peat moss, so check the label before you buy. They may instead contain other plant-based materials such as coconut coir (a fiber extracted from discarded coconut husks) ($17, Home Depot), recycled paper fibers, and compost. You can also try making your own mix from these alternatives.

None of these substitute materials work quite as well as peat moss. They certainly help, but don't result in such forgiving soil: with peat moss, you can underwater or overwater your plants, and they'll still be fine. With the alternatives, you may need to pay more attention when watering. "I think for gardeners, there's going to have to be a little experimentation to see what works best for them," says Chalker-Scott.

If you can't find a peat-free potting mix you like, you can look for the CSPMA logo on bagged mixes. When you see it, you'll know that at least there's been an attempt to restore harvested bogs. Even if it takes hundreds of years for the peat to regrow, the bogs are on their way to becoming functioning ecosystems again, even if they won't ever be identical to how they were before.

As gardeners, being more mindful of where all our materials come from will help us make a conscious choice about what to use and how much of it. Even though there's no one-size-fits-all solution for avoiding peat moss, there are more sustainable options for providing your potted plants with what they need to thrive.

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