Most every commercial potting mix contains sphagnum peat moss because it’s a good, lightweight, organic amendment that improves drainage, as well as water retention and air circulation. The downside to peat moss is that it isn’t a sustainable resource. Peat moss is the decomposing remains of living sphagnum moss, and it is harvested at unsustainable rates from bogs in a manner than involves scraping off the top layer of the living moss to get to the saleable product below.
This process destroys centuries-old bogs, doing away with wildlife habitat, releasing carbon dioxide into the air, and eliminating wetlands that help prevent flooding. Because of this, conservationists and scientists all over the world have been pushing for limits and even bans on peat moss harvesting.
In Britain, for example, where peat is often burned for fuel, harvesting has become so intense that the government has set goals for phasing out peat for home gardening use by 2020. Professional growers will need to go peat free by 2030.
Most of the peat used by the horticultural industry in the U.S. comes from Canada where talk of limits and bans is also heating up. So, whether you are concerned about the sustainability of peat of not, now seems like as good a time as any to explore some peat-free potting soil options.
Topping the list of sustainable peat alternatives is coconut coir. Coir is coconut husk fiber, a byproduct of the coconut industry in Southeast Asia where it is largely considered waste. Dehydrated and sold as small bricks or bales, coir can hold nearly 10 times its weight in water. Seriously, place one small, lightweight coir brick in a 5-gallon bucket and fill it half way with water, and you won’t believe how much light, fluffy coir you’ll have to work with.
Better still, recent research shows that coir performs as well, if not better, than peat when used as a soil amendment. Be aware that, like peat, coir is low in nutrients so it shouldn’t be used along in containers. It is also less acidic than peat.
You can buy peat-free potting soil mixes, which are slightly more expensive than peat-based blends, and consist primarily of compost, pine bark (or another type of bark) and coconut coir. Some mixes may also contain materials that help to improve drainage such as perlite (a type of volcanic ash) and vermiculite (a mineral that comes with its own set of environmental issues).
Make your own potting mixes
You’ll save money if you make your own peat-free potting soil. And it’s easiest to buy your ingredients and mix them in a wheelbarrow before filling your containers. I’ll save you the goose chase and tell you now that coir isn’t as ubiquitous as peat, so you won’t find it at all garden centers. You will find coir bricks online at a good price.
But if you’d prefer to shop locally, my favorite place to shop for earth-friendly gardening products is Mother Earth Gardens (www.motherearthgarden.com) in Minneapolis’ Longfellow neighborhood. They carry coconut coir bricks, as well as coir-based potting soil. Most of the local places that carry hydroponic growing supplies also carry coir. I’m sure other places stock it, too, but it’s probably a good idea to call ahead and check.
Once you’ve got your coir in hand, here are a few potting soil recipes that are easy, affordable and ensure good drainage.
For seed starting:
Wet coconut coir according to package directions and use as you would peat in trays or other containers.
1 part compost
2 parts coconut coir
1 part builder’s (sharp) sand
For ornamental plants:
1 part coconut coir
1 part compost
1 part good garden topsoil
1 part builder’s sand or perlite
2 parts compost
2 parts coconut coir
1 part builder’s sand
Keep in mind that compost is a good slow-release fertilizer. But container-grown plants, especially edibles, will need additional nutrients throughout the season. Some good choices include: additional compost, bone meal, vermicompost (worm poo), fish emulsion, fishmeal, cottonseed meal and alfalfa meal. And you’ll find most of these right on the shelves at local garden centers.
Get more gardening tips at Meleah’s blog: everydaygardener.com