Since Stephanie Rose found a way to make her own potting soil mix, the gardener has never gone back to those that rely on peat moss.
Sphagnum peat moss has long been a popular soil ingredient for gardeners, thanks to its ability to retain moisture and drain excess water to keep plants healthy. But the peat is harvested directly from Canada’s peatlands, degrading powerful carbon sinks that regulate Earth’s globe-warming greenhouse gases. Peat soil’s carbon footprint has inspired some gardeners, like Rose, to explore peat-free alternatives.
“Frankly, using this peat-free potting mix is so much better for the health of plants,” Rose said. She now mixes local soil with compost, ground coconut fibres — also known as coir — and rice hulls, which she buys from local breweries. She published her recipe in her book on gardening, Garden Alchemy.
“I’ve gotten wonderful little emails from people who have tried it and really, really liked it,” Rose said.
Peatlands, often composed of sphagnum moss, are hugely efficient carbon sinks that help mitigate global warming. Their soils contain more than 44 per cent of all the planet’s soil carbon, according to the International Union for the Conservation of Nature, despite only making up three per cent of the planet’s land surface.
In Canada, the horticultural peat extraction industry has about the same annual emissions as five gas-fired power plants — in 2021, according to Environment Canada, peat extractors released about 2.1 million tonnes of carbon dioxide equivalent into the air.
Some of the extracted peat ends up in the potting soil or bagged by itself at garden centres across the country. Rose said as she learned about the environmental impact of peat potting soil, she was inspired to try to find an alternative.
Rose is not alone. Across the world, gardeners are seeking out peat-free alternatives for plants at home. In the U.K., where about 80 per cent of peatlands have been damaged, England has vowed to ban the sale of peat for use in gardens by 2024.
Celebrity gardener Monty Don suggests using alternative mix-ins to help garden soils achieve similar drainage results without the peat. On his blog, Don says coir is an “effective” alternative. In a guide to gardening without peat, the New York Times describes coir as the “current poster child” of peat substitutes.
Gardeners are starting to avoid peat potting soils because of the carbon footprint of peat extraction. Across the world, these gardeners are exploring how peat-free alternatives let plants flourish.
Coir has its own carbon footprint. Peatland restoration researcher Mélina Guêné-Nanchen said peat is produced in North America, and shipping alternatives like coir from overseas also has a large emissions footprint. Plus, imported soil ingredients need to be treated to prevent the spread of pathogens.
At this time, it is not clear how coir’s carbon footprint compares to peat’s.
But there are also homegrown substitutes, some of which Don lists on his blog. He suggests collecting leaves, running a lawnmower over them to chop them into little pieces, stacking them in a heap outdoors and letting them compost to create a peat substitute. He says composted bracken, bark or pine needles also work.
In an interview with the New York Times, North Carolina State University horticulture expert Brian E. Jackson says wood fibres may soon become another effective soil mix-in.
Rose said her plants in peat-free soil have flourished. Rose said most plants prefer a neutral environment, and peat soils are more acidic than alternatives. Rose said for plants that like acidity, like blueberries, she uses soil straight from the ground — she lives in B.C., where the soil is naturally acidic.
Plus, Rose said, peat substitutes allow gardeners more forgiveness when it comes to watering plants.
“When you forget to water your pots, which everybody does, that peat in that soil mix will dry up and turn into a puck that’s difficult to rehydrate,” Rose said. She said the alternative soil mixes let gardeners forget to water once in a while without damaging plants.
“It’s a really superior peat potting mix alternative,” Rose said. “I use that exclusively in all of my gardens.”