Coir vs. Peat Moss

For many years, growing in containers has always been done with peat moss based soilless mixtures. Tradition, however, isn’t always the best approach. For starters, living in peat moss isn’t always what is best for your plants. Then there is the problem of it not being very earth-friendly.

No, peat moss isn’t toxic to the environment or a wide spread pollutant. It is however, an unsustainable product in that it doesn’t quickly replace itself. Bogs take many years to repair the damages done by harvesting peat. The process is disruptive to the ecosystem in place as well, though the peat moss industry will argue this point vehemently. It has other more damaging effects on our environment and is a huge contributor to climate change, but more about that in a bit.

In terms of your plant’s preferences, unless you’re growing with a hydro system or automated irrigation, peat dries out very readily. Once dehydrated, it is very difficult to resaturate, contributing to damage to foliage and roots for the home grower very readily. Coir on the other hand readily takes on moisture. Harvesting coir isn’t done for coir alone. It is the waste product of the coconut industry, and I do mean the waste.

The first thing a coconut harvester is concerned about is the food the oversized nuts contain. The oil is also of value for both food and skin products around the world. The shell is then processed for its valuable fiber, which is used to make rope. When everything of value that a coconut offers has been extracted, the remaining coir is nothing but trash. Recycling it for horticultural and agricultural use makes far more sense than draining massive tracts of undeveloped land so you can strip mine the part that nature finds useful… the portion that keeps unhealthy methane gas trapped and filters the water of connecting waterways and lakes. That’s what a bog does in the circle of nature. It’s purpose is not to grow greenhouse flowers, but to purify water. They don’t clear cut jungles to harvest coconuts.

The peat moss industry points its finger at the carbon footprint of coir. The pot calling the kettle black. All coir that arrives in North America, the UK or Europe is shipped by sea. In comparison, the peat moss industry uses a lot of fossil fuel harvesting and transporting the stuff. Peat moss harvesters are massive machines. They certainly aren’t hauling the raw material harvested from 40,000 acres in Canada every year with horse and buggy or fuel conserving micro trucks. The carbon footprint of moving from bog to processing or packaging plant and then out to millions of locations across the continent is incredible.

Then there are the problems of keeping the right pH balance for plants potted in peat based mixes, or seeds you’re trying to germinate in peat and peat pots. Most plants won’t grow in a bog, and its not just the water table. Ferns, some grasses and a few other plants that adore high acidity. So what do you suppose your sweeter soil natives like tomatoes, lettuce, peppers or geraniums are going to do in such an environment? The mix will contain limestone in an attempt to make the pH more desirable plant friendly, but every handful pulled from the bag will be different. The stone chunks are heavier than the peat or vermiculite in the mix and readily move around in handling and transit . Read the pH level stated on the bag. It will be a range, not a definite reading, because that is impossible.

If you’re using a hydroponic system, this unreliable pH level will give you far more problems than annual flower producing greenhouses experience. How will you keep your nutes in balance for the entire crop? Sure, in the early days of using coir for growing in containers, hydro gardeners had some issues with EC. The coir industry now washes the product and effectively lowers the salt content to make it a manageable potting material. Additionally, not all coir comes from coastal areas. You can get coir that has super low EC levels now.

Here’s an educated comment I found on a blog post about how peat is being done a huge disservice when people claim it is an unsustainable thing to use in your yard or containers. With all the other problems you can have when growing in peat, these fine points will easily steer you to choosing coir instead…

“Peat bogs are one of the planet’s largest and perhaps best ecosystems at long term carbon sequestering. Strip mining them not only releases that carbon, but huge amounts of methane which is a high powered greenhouse gas. It does so at the destruction of a species rich environment that does not bounce back with species diversity in any real sense. And with the destruction of the ecosystem there is an issue of “acid” runoff entering local waterways and impacting the fisheries.

Coir is a by-product from coconut plantations producing food and oil, as well as an extra commodity that brings in income from locally harvested “wild” trees in many locations. The husks being used for coir or fiber help raise the income of some of the world’s poorest people without jeopardizing their food production. And while a lot of Coir comes from south Asia and Indo-Pacific countries it is also being exported from Mexico and Central America. Modern Coir has very little salt issues, though when it first hit the market it certainly did. Since it is shipped via the ocean it has very low “carbon-points” due transportation and it would be interesting to see the energy input of that ocean freight, compared to the “carbon-points” of peat that is extracted using enormous diesel powered mining equipment and land based transportation. But those kind of numbers are hard to come by and I certainly can’t afford to pay for the impartial study.

I don’t think either product is really sustainable in the long term, but we all have to make choices that work for our gardens, houseplants and in my case business. I use more coir than peat… but I use both. We are testing using local rice hulls to replace both. Unfortunately while rice hulls make a great potting soil ingredient they do not hold moisture like coir or peat, nor do they seem to give any “grip” to the slow release organic nutrients we mix in to the soil… and we see much lower nutrient persistence in the pot. There is a “fluffed” rice hull option out there, but but I feel adding a factory process and the energy load that would take, sort of defeats the the whole idea. Hopefully using “lightly composted” rice hulls will make a difference.

But then trying to be “sustainable” is all about making choices that work for the task at hand, while taking in to consideration the impact of those choices make and making the best choice you can. After seeing peat bog strip mines in Canada and Alaska I choose to try not to use it.”