Coir vs. Peat Moss: What’s the difference?

When it comes to growing healthy plants, whether you are growing indoors or outside, the substrate in which your plants grow is an essential to the success of your ornamental plants or edible crops. Coir and peat moss are two natural products that both help to improve soil texture, improve aeration in compacted soils, increase water retention in sandy soils and encourage increased beneficial microbial activity. However, coir is commonly becoming a more popular choice over peat for a few important reasons.

What is Coir?

Coir is made from the fibrous layer of the coconut between the outer coat and the internal shell. It’s used in a variety of products including rugs, ropes, upholstery stuffing, floor matting and hanging plant basket liners. Over the last decade it’s become very popular with plant growers and gardeners for improving soils and creating growing media.

What's the Difference Between Coir and Peat Moss

Peat moss is often used to acidify and loosen soils, as well as for seed germination or lightweight potting mixes. Both peat and coir are equally good at improving air flow to roots, reducing fungal diseases and root rot.

Water Retention: For areas of the country where intense heat is an issue, coir is a great addition to soil because it can retain water up to seven times its dry weight. That’s roughly 30% more water than peat can hold. Add it to containers, hanging baskets and raised beds too to make water management easier. I also like to add it to my raised vegetable beds to keep water sensitive plants such as tomatoes from drying out too quickly in the heat.

Ease of use: Wetting dried peat to break apart and mix into the soil can be a challenge. Coir, however, breaks loosens up easily once exposed to water, making it fast and easy to use. Coir is an excellent amendment for soil that is compacted and needs increased air circulation and improved texture. Once saturated, you can keep it in closed containers for long periods of time and it won't dry out or get hydrophobic as can happen with peat.

Hydroponic Systems: Coir is a popular choice with hydroponic growers due to its ability to retain water better than peat, rockwool or perlite; and because of it’s solid root support and ability to suppress certain pests and diseases. Take note that coir is negatively charged and does have the capacity to hold nutrients; but that also means that nutrients can be bound up by the coir, leading to nutrient deficiencies. You’ll need to monitor your solution for pH and nutrient levels just as with any other substrate.

Pros of Coir

• Neutral pH
• Rehydrates easily
• Much less susceptible becoming hydrophobic
• Aerates soil
• Improves water holding capacity of soil/substrates
• Cation exchange capacity is higher than peat
• Renewable resource
• Easily stored as dry compressed bricks or blocks

Cons of Coir

• Ships from overseas (Sri Lanka, the Philippines, Indonesia, South America)
• Byproduct of deforestation
• Use to have high salt content, which required rinsing/buffering, but that is less of an issue these days.

Is Coir More Sustainable than Peat?

This is a topic of contention, depending on who you talk to and where you live. Technically, coir is a byproduct of the food industry and a renewable resource, whereas peat is not. By using it horticulturally this material is also kept out of landfills.

There is no "regrowing" peat bogs, which are areas of decomposed plant remains that have accumulated over thousands of years. Peat bogs are an important CO2 sink - trapping about 30% of ground CO2and when mined that CO2 is released into the atmosphere. Once it's harvested (called strip mining) it cannot be replaced, nor can those ecosystems that depend on peat bogs.

But, many will argue that there are many unsustainable characteristics of Coir, one shipping inputs and costs from overseas. The longer distance it has to travel to get to you the larger the carbon footprint. Coir is a byproduct of coconuts & oil palms farming, which takes a lot of land meaning forests are burned to create growing farms for such crops.

Either way, there are environmental impacts with both product. However, no one is growing coconut or palm trees for coir production. It's a waste byproduct. So, many consider Coir to be the better choice of the two.

One alternative to consider for both peat and coir may be PittMoss, however I've had both molds and fungi grow on PittMoss in moist containers. The fungi tends to be either harmless or beneficial, while molds can present problems for both your plants and you when used indoors.