Peat is an excellent growing medium for garden plants. But its use threatens the global environment

Over the past decade or more, environmentally conscious gardeners have reduced the amount of peat they use in their gardens, although the change hasn’t been quick or easy.

I wasn’t clear on all the reasons why gardeners should avoid peat until Tom Witwicki, president of the Cumberland County Master Gardeners Association, spoke at the Cape Elizabeth Garden Club last month about why the Using peat harms the environment and, just as important, how to avoid using it.

My wife Nancy and I have no recollection of buying peat moss balls for our outdoor gardens and pots, but many people have since the early 1900’s. Peat retains water and loosens the soil, which improves growing conditions for all kinds of plants – turf, perennials, shrubs and vegetables.
What we used – and still have on hand in our basement – ​​is Pro-Mix, a peat-based potting mix that is regularly used as a planting medium for vegetable and flower seedlings, as well as for potted plants of all kinds.

This is probably the last Pro-Mix we will buy.

Why is using peat bad for the environment, especially leading to climate change?

First, here’s some background.

The United States uses 1.4 million metric tons of peat a year, 70% of which comes from sphagnum bogs in Canada, Witwicki said. The peat currently mined comes from peat bogs formed during the last ice age.

Peatlands are important carbon sinks, that is, they contain carbon. But when peat is broken down in gardens or burned – peat is used as fuel in parts of Europe – it releases carbon dioxide, which helps trap heat near the earth’s surface.

Some other statistics from Witwicki: A cubic foot of peat contains as much carbon as seven pounds of coal. Peatlands cover only 3% of the land mass, but contain 30% of terrestrial carbon, more than all the forests in the world. Britain will ban peat cultivation from 2024.

Witwicki mentioned that the garden plants of member gardeners sold at the annual Cumberland County Master Gardeners meeting did not use peat – which is seen as a milestone for the major sale. He said calling it a peat-free sale requires an asterisk, because although master gardeners don’t use peat to repot their own plants, some seedlings sold at the sale may have been grown in potting soil containing peat. peat.

So if you can’t use Pro Mix or other products containing peat, what should you use? The go-to choice right now is coir, which is made from leftover coconut shells after the coconut has been processed to make various food products. Coco coir has a water-holding capacity similar to peat.

One problem is that coir is sold in fairly large bricks, which are virtually impossible to cut unless you have a bandsaw. Witwicki has one, but I don’t. The bricks need to be rehydrated, and if you use a whole brick (ours weighed 11 pounds), it will take almost a week for the coir to absorb enough water to use. The easiest way, and I use that word wisely, to do this is to put the brick in a wheelbarrow and fill the wheelbarrow with water. Once the coconut fiber has absorbed enough water, other ingredients should be added to it. To make peat-free potting soil, take seven parts rehydrated coir, two parts perlite or vermiculite, and two parts compost or worm castings.

Perlite is extracted from volcanic rock and helps soil retain water. Some people – including Nancy in this group – don’t like it because it’s white and doesn’t look like dirt. Vermiculite is a silica material, and is brown or beige.

Potting mix with coir, for sale at a local nursery. Photo by Tom Atwell

A recipe for a soilless seed mix is ​​eight parts coco, three parts earthworm, and four parts perlite.

Some premixed potting soils use coir. The most popular is called Mother Earth. But you will probably have to buy them online. I have rarely seen them locally.

I mentioned earlier that peat bricks are used as fuel in Europe. Nancy and I still have two peat bricks leftover after a friend gave us a dozen more than ten years ago after a trip to Ireland. We burned a few, but preferred the oak we got from fallen branches in our yard.

Maybe peat bricks will become heirlooms.

Tom Atwell is a freelance writer who gardens in Cape Elizabeth. He can be contacted at: [email protected]

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