My experiment with coconut-husk or coir mulch

The “before” picture – a block of compressed coir

Coir, which is the fibre from the husks of coconuts, is often recommended as a more environmentally friendly replacement for peat moss (whether it is or not is a topic for a different post). After yanking out some over-enthusiastic periwinkle, I had some bare soil that needed mulching, so thought I’d try out the sample of Miracle Mulch coir I’d received recently. It was an interesting experiment, though the jury’s still out on its effectiveness. Have you ever tried coir? Sound in on the comments.

In principle, adding water is meant to quickly make the block decompress. In practice, it took a fair amount of hacking with my Cobrahead to break the block up. Sort of like defrosting a block of hamburger meat in the frying pan, I had to flip the block over several times and chip off the “done” bits. The coir absorbs some, not all, of the water.
But it really does swell up, as you can see. The package says “increases 5 fold in 5 minutes.” Half of that statement was correct, in my experiment. The product is a mix of chunks and more fibrous bits.
It reminds me a little too much of red cedar mulch when new, but the colour does fade somewhat with time. One block lightly covered about ten square feet in my garden. I’ll report back after we’ve had the chance to live with it a bit.
And here’s the package, for more information.

7 comments

  1. Interesting. We have similar blocks here in the UK, but they're being marketed as growing media rather than mulch. I've had mixed results in that context, the coir definitely means less watering but it's hard to tell when that watering is needed.

  2. I had a similar experience to yours, Helen. It took some work to break apart the block of coir –definitely not 5 minutes. I used it as the base medium for a self-watering planter and it did seem to absorb a good amount of water and wick it up successfully to the soil above. I found that it did not break down and decompose as quickly as peat moss, which may or may not be a benefit depending on how you are using it. I am still not convinced, however, that transporting coconut fibre from the tropics is more environmentally friendly than using sustainably farmed and harvested peat moss from Quebec or the Atlantic provinces. I've visited one such farm in Quebec and was very impressed with how they managed this renewable resource.

  3. 1. Ignore the 5 minute marketing. When you let the coir soak for a longer period, say, over an hour, it does break apart very easily.
    2. I'm sure you don't use peat moss as a mulch. There's a finer, less fibrous, grade marketed as a soil amendment and/or potting mix component to replace peat . I found it to be unsatisfactory on its own for this purpose as it is too dense and waterlogged. However, mixed equally with the rougher, fibrous grade that is marketed as mulch (which you show), and some domestic compost, it makes an excellent growing medium. It is hydrophilic, unlike peat-based soil mixes, and as another commenter noted, it does not seem to break down anywhere near as fast as peat. This may be due it being very tannic – water draining from a planter using coir soil mix comes out stained deep red at first. Even now, at least five years later, the water drains out amber coloured; it still retains water very well, but is porous and aerated, and the antherium growing in it is very happy.

    1. No, you're quite right. Peat moss makes a lousy mulch – especially if gardeners try using it when it's dry (which actually sucks the moisture out of the soil). But thanks for your perspective on using coir as a soil additive and aerator.

  4. I am in costa rica with access to large amounts of free unprocessed husks right off the cocos. They just get dumped in fills and the folks are delighted if i would take some. Would like to try using them in my flower garden but no idea how it would work. Not sure how they break it down to the blocks you use. The husk fibres are long and stringy nothing like in your pictures. Any thoughts most welcome

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