Peat has long been a staple in gardening, especially in the U.S. and Canada. While it’s a widely discussed issue in the UK—where a retail ban on peat may soon come into effect—it’s still common in garden centres throughout North America. But the use of peat is becoming more controversial, and with good reason.
Let’s take a closer look at what peat is, why it became so popular, and why its environmental cost is now under scrutiny.
What Is Peat?
Peat is slightly decomposed organic matter—specifically, organic material from wetlands that accumulates and only partly breaks down over the course of centuries or millennia.
In gardening today, when we talk about peat, we’re almost always referring to slightly decomposed Sphagnum moss. While other types of peat exist, they’ve largely fallen out of use for horticulture. Sphagnum just turned out to be better suited to our needs. Other materials—dead plants, microbes, insects—end up in peat as well, but Sphagnum dominates.
Sphagnum mosses are a genus of plants—there are hundreds of species. Like other mosses, they don’t have roots. Instead, they absorb water and nutrients through their leaves and stems, and they’re equipped with specialized cells that can retain a lot of water—much like a sponge.
Why Does Peat Decompose So Slowly?
We’re used to seeing organic matter break down over months in a compost pile, but peat remains only slightly decomposed even after thousands of years. Why?
One reason is that peatlands are waterlogged, and the water contains very little oxygen. Microbial activity—the engine behind decomposition—slows dramatically without oxygen.
Also, peat is highly resistant to decomposition. It’s extremely carbon-heavy, with a high carbon-to-nitrogen (C:N) ratio—similar to straw. That means it lacks the “greens” needed to balance out decomposition. It’s essentially all “browns.” On top of that, Sphagnum moss acidifies its surroundings and doesn’t play well with others, creating conditions that further slow decomposition.
And many peatlands are in cold regions, where lower temperatures also reduce microbial activity—like your compost pile in winter.
Despite this slow pace, peat accumulates year after year—typically less than a millimeter annually in Canadian peatlands, or roughly the thickness of a credit card. But over centuries, it builds into deposits several meters thick.
Why Gardeners Loved Peat
We know organic matter improves soil—it enhances structure, drainage, aeration, and microbial life. But why did peat in particular become the go-to choice?
Water Retention
The first reason usually cited is peat’s ability to hold water. It’s light and fluffy, yet it can retain 15 to 20 times its weight in water—thanks to those sponge-like cells in Sphagnum. That’s a big plus, especially for seedlings.
The catch? If peat dries out, it becomes hydrophobic—water will bead up and run off rather than soak in. As long as it stays moist, though, it offers excellent water retention without making soil heavy.
Slight Acidity
Peat is slightly acidic, which benefits acid-loving plants. It’s sometimes recommended as a way to lower soil pH, and while that might work briefly, pH shifts from peat additions don’t last. Altering soil pH is a long-term, ongoing process.
Low Pathogens, Low Nutrients
Peat is often called “sterile,” but that’s the gardening version of the word—it just means fewer weed seeds and pathogens than your average garden soil. It’s not microbially sterile, but for organic matter, it’s relatively clean.
It also contributes little in the way of nutrients—which is actually a good thing in potting mixes where you want to control fertilizer inputs yourself.
Readily Available and Affordable
Peat is easy to find and relatively inexpensive, especially in Canada and the U.S. It’s mass-produced and distributed widely, so it became a convenient default.
A Brief History of Peat Use in Gardening
Peat was being recommended for gardens as early as the 1800s—initially as a soil amendment. It took longer to catch on in North America, but by the 1920s and ’30s it was showing up in agriculture and horticulture.
Its popularity soared in the 1940s and ’50s. A 1959 gardening book included over 400 references to peat. Rodale’s Encyclopedia of Organic Gardening, also from 1959, had more on peat than on peas, peaches, or pears.
Peat became the dominant base for potting mixes—a position it still holds. While we now mix it with other materials like perlite, peat remains the foundation.
The Environmental Cost of Peat
By the 1980s, environmental concerns about peatlands started getting more attention. These unique ecosystems turned out to be incredibly important, especially when it comes to carbon.
Peatlands store more carbon than all the world’s forests combined—about a third of all soil carbon globally. And this carbon got there naturally, over thousands of years, through the slow accumulation and preservation of Sphagnum peat under cold, acidic, oxygen-poor conditions.
But when we extract peat, we release that long-sequestered carbon back into the atmosphere. It’s the opposite of carbon storage—it’s carbon liberation.
Peat Isn’t Carbon-Neutral
Composting organic matter releases carbon too, but that carbon was only recently removed from the atmosphere by plants—it’s part of a fast-moving cycle. Peat, on the other hand, contains carbon that’s been locked away for centuries or longer.
Even with restoration efforts, peatlands don’t immediately start absorbing carbon again. It takes years—often decades—before a restored site becomes a net carbon sink. And it will take centuries, or longer, for the carbon content of those sites to return to pre-extraction levels.
Extraction Destroys Ecosystems
Extracting peat doesn’t just release carbon—it disrupts ecosystems. Restoration efforts today are far better than in the past, and often legally required, but even then, recovery is slow and incomplete.
“Restoration” doesn’t mean returning the site to its original state. It means making it ecologically functional again—at some level. If a decent amount of Sphagnum grows back, that’s considered a win. Getting tree cover and wildlife habitat back? That takes much longer, if it happens at all.
Studies have found that even when we transplant plants from healthy peatlands, many won’t survive in the degraded site. And collecting those plants degrades other peatlands—the “donor” sites. It’s a slow, resource-intensive process.
Isn’t Peat a Renewable Resource?
You’ll hear this a lot in peat industry PR: peat is renewable because it grows back every year. That’s technically true—another credit-card-thin layer forms annually. But that tiny growth doesn’t offset the damage caused by removing meters of peat.
Sustainability isn’t just about whether a resource is being replenished. In environmental terms, sustainability means meeting today’s needs without compromising the ability of future generations to meet theirs. Peat extraction fails that test.
What About Agriculture?
Peatland degradation for agriculture has been extensive—many times more surface area than what’s used for horticultural peat. But that’s mostly historical. Canada’s agricultural land peaked in the 1960s, and agricultural use doesn’t extract peat—it leaves it in place, though the land is drained and no longer functions as a peatland.
Horticultural peat, by contrast, is extracted—often to depths of five meters or more. And that’s still happening today.
Restoration Is Not Reversal
Peat supporters often point to restoration as a solution. But the timeline is long, and the results are limited. Restoration doesn’t reverse the release of centuries’ worth of carbon. It doesn’t fully recover the ecosystem. Even in best-case scenarios, it takes decades to achieve partial ecological function.
What Now?
Peat has served gardeners well for decades. But the cost is steep—both in terms of carbon and biodiversity. Restoration helps, but it doesn’t undo the damage quickly, and some effects may last forever.
The good news is: we have alternatives. Coir (from coconut husks), composted bark, wood fiber, and other materials are already being used. They come with their own environmental costs, but nothing like peat extraction. And while they may take some adjustment, thousands of gardeners have already made the switch—successfully.
We don’t need to give up quality to give up peat. We just need to adapt. And, given the stakes, that seems like a shift worth making.