Coir?!?

You may not recognize the word, but you’ve seen it in things like door mats, twine or brushes. Coir—pronounced COY-er or core, depending on who you ask—is the coarse fiber found between the outer husk of a coconut and the edible “nut” inside. It is sometimes called “coco peat” or “palm peat”, presumably because its color and horticultural usage is similar to sphagnum peat moss.

The coconut palm (Cocos nucifera) has been in cultivation for at least 4,000 years, not just for food but just as importantly for fibers, fuel and building material. Not surprisingly, coir has played an important role wherever coconut palms are grown, mostly as the raw material for rope and twine. Click here to read an interesting article on the history and making of coir.

The use of coir for horticultural purposes is relatively new. Traditionally, peat (sphagnum peat moss) has been used to aerate and lighten heavy soils and to improve the water retention of sandy soils. In fact, many if not most commercial potting soil mixes on the market today contain at least some peat. The problem with peat is that it is not a renewable resource and is being harvested at non-sustainable rates.

Coir is being touted as a viable alternative since it is a by-product of coconut production and completely renewable. It is much easier to wet than peat (if you’ve tried to wet dry peat, you know how difficult that can be), holds water just as well if not better, decomposes more slowly and doesn’t get compressed like peat does. In addition, the pH of coir is more neutral than peat so it doesn’t change the pH level of the medium to which you add it.

I became aware of coir when researching potting soil mixes for succulents. Many commercial cactus mixes are surprisingly high in peat. Once the soil is dry, it is very hard to rewet it; this results in a lot of wasted water and, on my part, in a lot of frustration. I decided to give up completely on commercial  cactus mixes and make my own, based on the experience and recommendations of other succulent growers.

Many growers use coir in varying proportions in their soil mixes. Since coir has a stable, open structure that allows plenty of air to get to the roots, it is an ideal amendment to create a loose and well draining soil mix. Combined with at least 50% pumice, perlite, calcinated clay or the like, coir with its superior water-holding capability ensures that the mix doesn’t dry out too quickly, yet at the same time doesn’t subject the roots to an excess of much moisture.

After digesting the information I found online and in books, this is the soil mix recipe I’ve settled on: 50% pumice (in the form of Dry Stall, a horse bedding product sold in feed stores), 25% coir and 25% commercial potting soil. I will give this a try for all potted succulents, starting—well, as soon as my coir is ready to use.

Coir block

Coir typically comes in compressed bricks that are surprisingly heavy. According to the instructions I received for the bricks I bought, “simply place the brick in a bucket of water and walk away”. Well, I did just that, 24 hours ago, and half the brick is still, well, a brick. But what has come off—in no small measure due to my whacking, prodding and scratching with a cultivating mattock—is beautifully fluffy and fiber-y.

Coir after rehydration

Another day or three, and my coir should be ready to go. I can’t wait to make up my first batch of succulent potting mix. My golden barrel cactus would really like a new home!

High-fiber diet for the soil