Should We Be Cutting Back on Peat Moss?

April 5th, 2022

   Peat moss has long been our go-to, store-bought, plant-growing medium, useful for everything from starting seeds to growing potted plants to “lightening” our lousy clay soil.

Most potting mixes are heavily composed of peat moss.

   But its widespread use is under fire lately as some argue that gardeners should move away from peat moss altogether for environmental and climate-change reasons.

   The main issue is that peat moss serves as a super-sponge when it comes to soaking up carbon that otherwise would end up in Earth’s warming atmosphere.

   Although peat bogs cover just 3 percent of the Earth’s surface, they store more carbon than all other vegetation types in the world combined – including trees – according to International Union for the Conservation of Nature.

   Harvesting peatland bogs reduces that layer and sends peat out in forms that are burned as fuel or that quickly decompose in gardens, releasing the stored carbon into the air.

   Fossil fuels also are burned in harvesting and transporting all of the peat, plus harvesting reduces a natural land use that harbors rich biodiversity, mitigates drought, and heads off wildfires.

   The whole issue is especially heated in Great Britain, which is phasing in a ban on most forms of garden-use peat after some 90 percent of its once expansive network of peat bogs has been harvested or degraded.

   Some in Britain, including the Royal Horticultural Society and its best known gardener, TV celebrity Monty Don, are doubling down on a quick end to peat use in gardening.

   Don, for example, calls peat-harvesting “eco-vandalism” and flat-out says, “Gardeners should not be using peat… There is no need. There are plenty of alternatives to peat.”

   Here as there (and despite the alternatives), it’s not easy convincing gardeners to give up such a staple product – especially considering that not even the horticulture industry and many of its leading experts and growers are convinced this is something we need to do.

   While most agree it’s not a problem switching to other choices for improving garden soil, many argue that it is a problem finding comparable alternatives to peat moss for potting mixes and seed-starting mixes.

   Peat moss became so popular in the first place because it offers so many growing benefits, including being porous, organic, good at holding an ideal mix of moisture and air, generally free of weeds and diseases, and relatively inexpensive.

   It’s by far the leading ingredient in most bagged potting soils and container mixes, and it’s widely sold in compressed, rectangular bales at box stores and garden centers for gardeners who are trying to improve poor soil or build new raised-bed gardens.

   Peat moss results from the very slow breakdown of organic matter under acidic and low-oxygen conditions, usually in cool- to cold-climate regions.

   Most of the peat moss that American gardeners use comes from vast peat bogs in Canada.

This is a peatlands field in Ireland.

   The Canadian Sphagnum Peat Association says that unlike Great Britain, Canada’s peat supply is nowhere near being depleted with only a fraction of a percent of its 279 million acres being harvested or under harvest. And only a small fraction of that ends up in bags and bales for home gardeners.

   Wetland ecologist Dr. Merritt Turetsky, social media’s “queen of peat” and the director of the University of Colorado’s Institute of Arctic and Alpine Research, counters that we have plenty of other non-peat choices for gardening and that we ought to keep every bit of peat that we can in its place.

   “Peatlands are some of the world’s most powerful stockpiles of carbon – carbon that we do not want back in the atmosphere,” Turetsky said in a recent Joe Gardener Show podcast. “Let’s learn from what the U.K. learned and choose to do something different.”

   Opposing sides of the equation don’t even agree on whether peat is “renewable” or not.

   Peat-protectors like Turetsky say nature needs centuries to replenish a harvest of peat, while the industry says that peatlands can be restored at a rate of more than two inches a year by seeding harvested land.

   If you’re leaning toward the cutting-back/cutting-out camp, what are your peat alternatives?

Homemade compost is an excellent peat alternative for improving garden soil.

   The quickest and easiest change is to switch away from peat bales for your in-ground soil improving.

   The best alternative there is using your own homemade compost, which not only is an ideal amendment texturally and nutritionally but takes advantage of recycled organics from around the yard and house. That also cuts out transportation costs and removes leaves, grass clippings, kitchen peelings, coffee grounds, and such from the waste stream.

   The second best alternative is using leafmold from municipal leaf collections. Many of our area towns and townships compost leaves and offer this black gold back to residents – usually at no charge if you go and get it.

   A third option is using retail-bought, non-peat bagged or bulk organic amendments. These include commercially made compost, mushroom soil (decomposed manure and straw or sawdust from mushroom production), and rotted horse and cow manure.

   For seed-starting and growing potted plants, more and more non-peat bagged brands are becoming available – although you still might have to poke around a bit to find them and usually pay a bit more.

   Look on the bags for labels that say “peat-free,” or check the contents list to determine what’s in the bag.

Coir is ground-up coconut-hull fibers.

   Chester County’s Organic Mechanics is one of the more widely available non-peat brands, containing assorted peat alternatives as compost, finely ground pine bark, coir (the ground-up fiber from coconut hulls), worm castings, rice hulls, and/or perlite.

   PittMoss is another product that’s become popular in the Pittsburgh area where it’s made and is just starting to show up in other parts of Pennsylvania. The brand, which got a boost from celebrity investors on The Shark Tank TV show, is made mostly out of recycled newsprint with a small amount of organic bark, poultry manure, and feather meal.

   Beyond Peat and Back to the Roots are two other peat-free brands starting to make national headway in box stores.

   A third strategy is to either make your own potting mix out of individual ingredients or to reduce/dilute peat usage by mixing non-peat ingredients into traditional peat-containing mixes.

   Dr. Jim Downer, a University of California plant pathologist who has tested scores of retail potting mixes, says one good homemade potting mix is using 50 percent coir, 25 percent finely chopped bark, and 25 percent perlite along with a small amount of organic fertilizer or timed-release fertilizer.

   University of Maryland Extension educator Jon Traunfeld suggests a blend of coir and compost – ranging from half of each to a blend of three parts coir to one part compost.

   And Jessica Walliser, author of “Container Garden Complete” (Cool Springs Press, 2017, $30), recommends a DIY mix using six gallons of coir, four-and-a-half gallons of perlite, six gallons of compost (ideally from your home bins), and one-and-a-half cups of a granular organic fertilizer.

   Or simply mix 20 to 30 percent compost or up to 50 percent coir into a bagged, store-bought potting mix to reduce your peat use.

   North Carolina horticulturist and “Foodscaping Revolution” author Brie Arthur says she’s had good success growing edibles in pots filled with 100 percent compost that’s made out of one-third straw, one-third grass clippings, and one-third composted cow manure. She notes that compost-filled pots will be much heavier, though, than ones filled with traditional peat-based mixes.

   Good alternatives are tougher to find for seed-starting, where peat moss still reigns supreme. Peat-based mixes can be diluted with additional perlite and/or coir, but one potential drawback to coir is that it may have a high enough salt content to harm young seedlings.

   That’s less of an issue recently since most coir producers wash the fibers to reduce salt levels, according to the University of Washington Extension.

   Michigan State University Extension says one good DIY seed-starting mix is one-third coir, one-third finely screened compost, and one-third vermiculite.

   Oregon State University Extension recommends a similar blend of one-third coir, one-third compost, and one-third sand, vermiculite, or perlite.

   Dr. Brian Jackson, who’s researching soilless growing mixes at North Carolina State University’s Horticultural Substrate Laboratory, said in a recent Margaret Roach “A Way to Garden” podcast that wood fiber is another promising peat alternative in growing mixes.

   With any alternative, he added, it’s important to go slow, experiment, and compare because different mixes may need different watering and fertilizing regimens than familiar peat-perlite blends.

Read more on DIY potting mixes in a post I wrote in May 2021 for PennLive.com.