Peat has been a go-to material in gardening for decades. It’s especially common in potting mixes used for houseplants, container growing, and even raised beds. But its use has become increasingly controversial, and for good reason.
This post focuses on peat use in the U.S. and Canada. It’s a well-known issue in the UK, where a retail ban has been proposed (and delayed), and the Royal Horticultural Society has announced that it will be banning peat at its shows.
What Is Peat?
Peat is slightly decomposed organic matter. More specifically, it’s organic matter from wetlands that has built up and partly broken down over centuries or even thousands of years.
When we talk about peat in gardening today, we’re almost always referring to slightly decomposed Sphagnum mosses. Other types of peat exist, but they rarely come up anymore. Sphagnum peat proved to be better suited for gardening than the alternatives. Other organic matter can get into the peat—bits of dead plants, microbes, insects—but it’s mostly Sphagnum.
Sphagnum mosses are plants—like all mosses. Taxonomically, Sphagnum is a genus with hundreds of species. Mosses don’t have roots. They absorb water and nutrients through their leaves and stems, and they have specialized cells that hold a lot of water—like a sponge.
Why Does Peat Decompose So Slowly?
In a compost pile, we expect organic matter to decompose within a few months to a year. So how is it that peat remains only slightly decomposed after centuries?
There are a few reasons. First, peatlands are wet and waterlogged, and the water contains very little oxygen. There’s oxygen in water molecules, but not much dissolved oxygen. That lack of oxygen greatly reduces microbial activity, which drives decomposition.
Peat is also resistant to decomposition because it’s very carbon-heavy. Its high carbon-to-nitrogen (C:N) ratio is similar to straw. We don’t usually think of moss as a “brown” in composting terms, but it is. There’s not much nitrogen to balance things out, which slows decomposition even further.
On top of that, living Sphagnum mosses create acidic conditions. They don’t play well with other species, and their acidity also slows decomposition.
And many peatlands are in colder areas, where microbial activity slows down—just like in a compost pile during winter.
So even after centuries, peat only decomposes a little. Meanwhile, more is added every year as mosses reach the end of their life cycle. In Canadian peatlands—the source of most of the peat sold in the U.S.—peat accumulates at a rate of less than a millimeter per year. But over hundreds or thousands of years, that adds up to deposits several meters thick.
Why Has Peat Been So Popular?
We know organic matter benefits soil. It improves structure, drainage, aeration, and supports microbial communities. But what made peat in particular so widely used, especially since the 1950s?
Excellent Water Retention
Peat is light and fluffy—great qualities for a potting mix. But for something so light, it holds an impressive amount of water—typically 15 to 20 times its weight. That’s thanks to those specialized cells in Sphagnum.
This water-holding capacity is especially helpful for seedlings but beneficial for all plants.
There is a downside: when peat dries out, it becomes hydrophobic. Water will bead up or run off instead of soaking in. So you have to avoid letting it dry out completely. But as long as it stays moist, peat keeps soil wet longer while still allowing air to circulate—ideal for container growing.
Slightly Acidic
Peat is naturally a bit acidic, which makes it well-suited for plants that prefer acidic soil. It’s sometimes claimed that peat can lower your soil’s pH, and it probably does—briefly. But changing your soil’s pH is a never-ending process, and whatever effect peat has will be short-lived.
Fewer Pathogens and Weed Seeds
Peat is often described as “sterile,” though that’s the gardening use of the word. It’s not sterile in the microbiological sense, but likely contains fewer pathogens and weed seeds than compost or garden soil.
It also provides almost no nutrients—which is fine in a potting mix, where you’re adding fertilizer anyway. You don’t have to account for any nutrient contribution from the peat.
Widely Available and Inexpensive
Peat is easy to find in garden centers and online, and it’s not very expensive. There’s clearly a lot of it being produced and sold.
Put all that together, and it’s no surprise that peat became so widely used.
Peat’s Long History in Gardening
Peat was already being recommended to gardeners in the early 1800s, mostly as a soil amendment. It took longer to become common in the U.S., but by the 1920s and ’30s it was being used in agriculture and horticulture.
Its popularity really took off in the 1940s and ’50s. A 1959 edition of 10,000 Garden Questions Answered by 20 Experts mentioned peat over 400 times. That same year, Rodale’s Encyclopedia of Organic Gardening included over 200 references to peat—and its entry for “peat” was longer than the ones for “pea,” “peach,” and “pear.”
Peat became the king of potting mixes, and it still holds that position today. We usually mix it with other materials like perlite, but peat remains the base.
The Environmental Concerns
Starting in the 1980s, people began asking more questions about peat’s environmental impact. As we learned more about peatlands, their ecological importance became clearer—especially their role in carbon storage.
Peatlands as Carbon Sinks
Peatlands are one of the best places on Earth to keep carbon stored in the ground and out of the atmosphere. They hold more carbon than all the world’s forests combined. About one-third of all soil carbon is stored in peatlands.
That carbon built up naturally over thousands of years, thanks to the slow decomposition of Sphagnum in wet, oxygen-poor, acidic, often cold conditions. If left undisturbed, peat continues to decompose slowly and hold onto its carbon for many more years.
Peat Extraction Releases Carbon
When we extract peat, we’re releasing carbon that had been safely sequestered for centuries. Some people prefer to call it “harvesting” or “mining,” but whatever the term, it’s indisputably extraction.
We talked elsewhere about how composting releases greenhouse gases too—but compost is made from recently living plants. Peat is made from organic matter that’s been buried for millennia. So its release of carbon isn’t part of a short-term cycle—it’s reopening the vault.
Peat extraction is about as far from carbon-neutral as it gets. And while degraded peatlands may release less methane (another greenhouse gas), that benefit is far outweighed by the carbon dioxide emissions. And that’s without even counting the emissions from the extraction process, processing, and transportation.
Destruction of Ecosystems
Peat extraction also destroys ecosystems. Restoration efforts have improved dramatically in recent decades, and in many cases they’re legally required. But even in best-case scenarios, restoration takes decades—and it doesn’t mean the site returns to what it was.
In ecology, “restoration” usually means making a site function again at some level—not replicating its original condition. If Sphagnum moss covers even part of the ground, that’s considered a success. It might not be close to the original ground cover. And while it’s great when other vegetation and wildlife return, that could take decades, if it happens at all.
Even after peat extraction stops, it can take many years before the site begins holding more carbon than it releases. And getting back to its original carbon levels? That’s a timeline of centuries or longer—possibly thousands of years.
Restoration Has Limits
Even with today’s improved restoration techniques, many native plants won’t grow back. Studies have shown that up to 20 percent of transplanted species fail to establish—even when taken from similar environments. Until recently, that 80 percent success rate was an ambitious goal. A 2013 study found that 43% of restored sites had failed to become Sphagnum-dominated ten years later.
And the restoration process itself requires donor material—taken from healthy peatlands, which are then degraded in turn. Those donor sites may take years or decades to recover.
The Scale of the Problem
In the UK and Ireland, about 80 percent of peatland has been degraded. Across Europe, the figure is about 50 percent—the highest of any continent. Peat was historically a widely used fuel source, which contributed to this degradation.
In North America, the damage has been more limited—at least so far. The U.S. gets around 90 percent of its horticultural peat from Canada, and only about 2 percent of Canadian peatlands have been degraded. But much of Canada’s peatland is remote, hard to access, or located in arctic and sub-arctic areas. Many of these lands are on Indigenous territories, where extraction faces significant resistance.
So while the overall percentage degraded is low, most of the accessible southern peatlands have already been affected.
Misleading Defenses of Peat Use
The peat industry has mounted PR campaigns to defend continued horticultural use. These efforts often target science-minded gardeners with what appears to be rational, fact-based messaging—but relies on selective facts.
“Peat Is Renewable”
It’s true that peat continues to form—about a millimeter per year. But that doesn’t make it renewable in any practical sense. That tiny layer doesn’t come close to offsetting the ecological damage of removing several meters of peat in one go.
In environmental terms, sustainability means meeting today’s needs without compromising the ability of future generations to meet theirs. Peat extraction does the opposite—it provides short-term benefits while causing long-term harm.
“Agriculture Is Worse”
It’s also true that more peatland has been degraded for agriculture than for horticulture. But that doesn’t excuse current peat extraction. Most agricultural conversion happened decades ago. Canada’s total agricultural land peaked around 1966.
And unlike horticultural extraction, agricultural conversion usually leaves the peat in place—drained, yes, but not removed. Horticultural extraction digs meters deep and continues today.
“We Restore the Sites”
Restoration is cited as a solution, but its challenges are often downplayed. Even successful restoration doesn’t return the site to what it was. It’s a long-term process, and the damage—especially the carbon release—can’t be undone.
Moving Forward
Peat has had a long run. It offered real benefits—especially for container growing—and became the default base for potting mixes.
But its environmental costs are steep. Restoration helps, but takes decades. And no restoration undoes the release of sequestered carbon built up over thousands of years.
This is a long-term sacrifice for a short-term gain—the very opposite of sustainable.
The good news? Gardeners around the world have shown that change is possible. And the more we understand the consequences, the clearer the case becomes.