Thursday, June 10, 2021

Should We Stop Using Peat in Our Gardens? by Nancy Shepard


PhotoPete Stuart (Shutterstock)

[Extracted from Washington Post article May 11, 2017 and LifeHacker June 7, 2021.] 

Virtually all of the peat moss sold in the United States comes from the vast sphagnum moss bogs of Canada. Often mixed with a mineral named perlite, it is highly valued by horticulturists for its ability to retain moisture and oxygen without becoming waterlogged or heavy. It is generally sterile and naturally suppresses a fungal disease that can afflict seedlings, making it a natural choice for seed starting. So why should we avoid using it?

So why would Mark Highland, owner of Organic Mechanics in Modena, Pa., go to considerable trouble to avoid it? “I think the average gardener has no idea what peat moss is, where it comes from and whether they should even consider an alternative,” Highland said.

Peatlands store a third of the world’s soil carbon, and their harvesting and use releases carbon dioxide, the major greenhouse gas driving climate change. The biggest environmental risk from peatlands is if they catch fire, which happened spectacularly in 2015 in Indonesia on land cleared for plantations. Peatland fires account for up to 5 percent of human-caused carbon emissions, according to the United Nations, which last year launched a peatlands conservation initiative.

For horticultural use, the extraction of peat requires the removal of a bog’s living surface to reach the partially decomposed layers beneath. It grows at a mere sixteenth of an inch a year, and its mining removes layers that take centuries to develop. “Peat is the best vegetative carbon sink we have on the planet,” Highland said. “Why dig it up?”

What is peat doing for your plants?

It has a remarkable ability to efficiently manage water  and hold on to nutrients that would otherwise leach out of the soil. While performing these amazing tasks, it also improves the texture and consistency of the soil.

Although peat is used in many soil mixtures, it may not be an adequate option for root growth and often needs to be mixed with the material perlite to even work. Ken Druse with The Garden Rant writes, “peat moss is a poor choice. It breaks down too fast, compressing and squeezing air out of the soil, creating an unhealthy condition for plant roots.” Peat, when added to soil, is touted for its ability to hold in moisture and bring vital hydration to the plants, but the fast rate of decomposition means the pros do not outweigh the cons.

In Britain, for example, using peat has become taboo. The government’s environmental agency has said it wanted to phase out peat moss for hobby gardeners by 2020 and commercially by 2030. The London-based Royal Horticultural Society, the largest gardening organization of its kind in the world, has reduced peat use by 97 percent at its four major gardens and urges its members to follow its lead.

But is it sustainable?

Canadian peat producers say that the mining of peat is sustainable and that harvested bogs are returned to living sphagnum moss peatland after five years. (Quebec Peat Moss Producers Association)

Paul Short, the group’s president, said that for the past 10 years, producers have been restoring harvested bogs by allowing them to re-flood and seeding them with shredded moss grafts that grow and knit together. The moss covers the harvest site within five years, he said, and the bog is “back to a near-natural condition within 10 to 15 years,” he said.

Cutting turf on Achill Island. Ireland’s 
Photo: The Guardian
In northern Europe, dried peat has been used for centuries as fuel — raising its profile as a source of atmospheric carbon dioxide — and people live closer to ancient bogland that has been drained for agriculture and development. In Canada, by contrast, peat isn’t used as a fuel, and its sheer acreage in less populated areas works in favor of its mining. Canada is the second-largest country on Earth and has 25 percent of the globe’s peatlands. The bogs are drained before harvesting, and the top layers of peat are mined with a large vacuum apparatus.

Peat alternatives

So what can we use instead? 

Compost: Compost is made from rotted plants, green waste and animal manures. It is inherently renewable, and making your own is cheap and minimizes your carbon footprint (no shipping). The rub is that compost takes time and skill. Authentic compost is a careful blend of nitrogen and carbon sources, turned frequently, kept moist but not wet, and screened for use — all reasons to buy high-quality bagged compost. Most backyard compost piles are merely aging piles of organic matter that don’t get hot enough to kill weed seeds or pathogens.

Coconut fiber: Coconut fiber, called coir, is a byproduct of fiber processing and has become a favored alternative to peat moss over the past 20 years. India, Sri Lanka and Vietnam are centers of production. It has the same water holding and porosity of peat moss, though it is generally used as one ingredient in a mix.

Its distant origins raise questions about the carbon footprint of its shipment to the United States. In addition, it derives from coconut plantations that may have been carved out of rain forests, Short said. “Yes, it’s a byproduct, but this isn’t Tom Hanks wandering around an island picking up coconuts,” he said. “These are plantations.”

Pine bark: Finely shredded and composted pine bark (not pine nuggets, pine needles or pine mulch) is a valuable substitute for peat moss as part of a mixture.

PittMoss: PittMoss was created by an inventor in Pittsburgh and consists of reconstituted paper fibers with added proprietary ingredients. It can be used alone or mixed with potting mix, based on the product used.

Rice hulls: Sterilized rice hulls are not a substitute for peat moss but replace perlite and vermiculite, the production of which requires fossil fuels.

Worm castings: This is the waste from farmed earthworms, rich in nutrients and beneficial microbes, and used as a common ingredient in peat-free mixes.

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