Substituting coir for peat moss

Judith Adam

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Coir can be used as an alternative to peat moss.

One of the benefits of belonging to plant societies is receiving their informative journals. The December 2012 journal published by the Cyclamen Society ( in Great Britain has an article entitled, “A Decent Peat-Free Compost,” by the society’s treasurer, Keith Fry. Many gardeners are eager to learn more about using coir as a substitute for peat moss, so I’ll share some of his information.

According to Fry, harvesting peat moss from bog deposits endangers the plants and animals that rely on bog habitats, and bogs are virtually non-renewable. (For an update on the status of peat bogs in Canada, see “Give Peat a Chance” in Garden Making # 11, Fall 2012.) Substituting coir for peat moss is a viable solution, he writes.

Coir is a layer of plant fibre contained in the husk of coconuts, and has similar properties to peat moss. It’s also renewable and appropriate for garden use. “The coconut is botanically analogous to a plum, but instead of fleshy material enclosing the hard-shelled seed, the outer material, called coir, is the waste product of coconut cultivation,” Fry writes. Commercial coconuts for export are an important crop in India and Sri Lanka, and some people claim the economies of both countries would benefit from an increase in demand for horticultural coir.

I have a one-litre block of coarse-grade compressed coir on the shelf in my basement (purchased for repotting orchids), where it has been waiting for me to become enlightened on how to use it. When soaked in a bucket of hot water, the compressed block will expand to about six or seven litres of material. Coir is also available loose, as a fine-milled grade, packaged in 35-litre bags for garden use (look for that in garden centres next spring).

Coir ranges between 5.5 to 6.5 pH, not quite as acidic as peat moss, but still a good product for planting rhododendrons and roses. These both appreciate generous amounts of organic material around their roots. Coir also compares well with the water retention capability of peat moss, and improves drainage and oxygen retention.

Fortunately, Fry gives his recipe for substituting coir in his own planting mix, as follows: five litres of reconstituted coir, five litres of recycled green waste (such as leaf mulch or homemade garden compost), 25 grams of pelleted slow-release fertilizer, and 0.5 litre of perlite or coarse grit. This would make an excellent potting soil, and could be prepared in larger quantities to use in planting holes. Thanks, Keith Fry, for sharing your recipe.

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8 thoughts on “Substituting coir for peat moss”

    • Hello Dorothy,
      Coir products are usually available in the garden departments of hardware stores and building-suppy stores in the spring. I usually find the bricks with the seed-starting supplies. If mail-order is more convenient, look at the Veseys seed catalogue. It’s available online at

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      • Judith, I understand that coir naturally has salt (sodium chloride) in it. Any comments on this? Is it an issue for plants and orchids? Are current products on the market washed or require washing/rinsing to eliminate the salt? Additional detail would be helpful. Cheers!

        • Hi Stephen,

          You raise an interesting question about potential sodium chloride content in coir. As I understand the issue, the coconut fibre (and its mother plant) are free from excessive sodium. However, the processing of coir fibre raises opportunities for sodium to contaminate the coir, particularly if sea water is initially used to wet the fibre and prepare it for packaging. When fresh water is used in processing, there is no sodium transference. Unfortunately, the source of water used in processing isn’t part of the package information.

          So what to do? A reputable company will be sure to supply coir that isn’t high in sodium chloride, and we should purchase coir supplied from a company we recognize and trust. When using coir from an unfamiliar source, soaking the fibre in water will leach out any sodium present. To do that, just add more water than the coir can absorb, let it sit for a few hours, and then drain away the excess. A wheelbarrow or child’s plastic swimming pool is good for this job. The soaking in water will efficiently remove sodium and, of course, coir should be combined with other potting materials, like compost, leaves and sand.

          So far, I haven’t found an example of any plant being damaged by sodium chloride in coir. I think it’s a good product and safe for plants.

          — Judith

          • Hi Judith

            Coir has high levels of sodium in it mainly from the water used to process it but also from the plant itself. A palm tree is one of the most salt-tolerant plants. You need to be quite careful where the coir comes from; most “clean” coir is used by the professional growers. It’s very debatable if it’s friendlier then peat moss. Check out the Canadian sphaghnum peat producers’ website for some interesting facts about peat moss. Also coir is used as a heating fuel for cooking in many of the coir-producing regions. Many of the countries producing coir have limited fresh water and should be using it for other higher priority items like food processing.

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