First coir

[fanaticactus]

I just received my first supply of coir today and soaked some in water to expand it. It's drying out a bit (hopefully) tonight for use with pumice and some grit. I noticed that this particular coir appears to be more finely chopped than what came (surprisingly) in my last two cacti from the garden center. That coir was quite fibrous and it allowed for incredible root development. Does more finely milled coir behave differently in a substrate than the long, thin fibrous type? Does it pack more densely and stay wet longer? I've looked online at about five sources and they all recommend different proportions of pumice and coir. I'd like to know if our members have any "magic" percentages they've had luck with. Thanks.

[fanaticactus]

No help? I'll just start with a small amount, then. Not knowing how finely milled coir behaves and how much water it holds and how much it might compact, I'll just start with a small percentage mixed with pumice and grit.

[DaveW]

Never used it I'm afraid, but found these on the Web:-

http://www.canna-uk.com/growing_with_coco" onclick="window.open(this.href);return false;

http://www.succulentsandmore.com/2011/1 ... g-mix.html" onclick="window.open(this.href);return false;

[greenknight]

It seems to me that the main effect of milling it would be to make it easier to work with. Breaking it up in small pieces might allow it to soak up water a little faster, but shouldn't change its properties otherwise.

[DaveW]

It really depends how fine it is, whether it is fibrous or mainly dust? Texture and fineness does affect drainage to some degree, after all sand is only very fine grit, but a potting soil including sand does not drain like one made with grit instead. I would suggest you do an experiment to see what proportions of coir/pumice/grit have the drainage characteristics you want. I find making transparent pots by cutting off the lower parts of plastic spa water bottles or similar and punching a drainage hole in them allows you to see how quick the various mixtures drain and dry out when placed side by side in the same conditions.

[fanaticactus]

These will be good tests for the future. I repotted those cacti that had been without pots for a while two days ago. I decided to use a mix of 60% pumice, 20% coir and 20% a combination of DE (Oil-Dri) and porous aquarium grit. Then I threw in another part of sharp grit. The mixture seems quite light and the coir is well mixed through and should not clump. I know I'll have to wait a week or two to water them; I want to water them before summer is over so they can get "settled" in the new pots before the colder weather arrives and I have to stop watering for their winter rest. I will not be able to repot my entire collection in this better mix, so I'm choosing the ones that showed no growth this past year and the ones whose pots don't give when I squeeze them due to their soil that became too hard packed. I'm hoping I'll have more winter survivors than last year.

[DaveW]

Hopefully the American winter will be better this time than last year for some of you, however we has a mild winter last year so hoping ours is not a lot worse this time in the UK.

[greenknight]

Coir is a bit different from sand, it's porous and has a rough surface no matter how small you chop it up. It's lightweight, and much more "sticky" than sand grains. It gets heavier when it absorbs water, but it also swells,so it's less able to sink down in the mix.

The type of grit you want in cactus mix consists of coarse, irregularly-shaped bits of mineral - the irregular surface keeps them from packing tightly together, makes them "sticky" so they don't sink. Fine sand contains a lot of tiny quartz crystals - rather smooth, pack tightly, and easily sink down through the mix, not "sticky" at all.

Coir would have to be ground so fine that its cell structure was destroyed before its properties would be much altered, which I can't picture anyone doing. Milled coir might break down a little faster than coarser grades, but that shouldn't be much of a problem; potting soil eventually needs to be replaced, anyway.

Testing how your mix drains is a good idea, though.

[fanaticactus]

Coir is a bit different from sand, it's porous and has a rough surface no matter how small you chop it up. It's lightweight, and much more "sticky" than sand grains. It gets heavier when it absorbs water, but it also swells,so it's less able to sink down in the mix.

This is the type of information I needed to hear. As long as it remains effectively mixed with the pumice, DE and grit so that it doesn't form a solid mass like dried peat, it's what I'll be looking for to allow the roots to breathe and grow. Thanks for this explanation, greenknight.

[Rod Smith]

I've used coir exclusively as the main constituent of my cactus & succulent compost for the past three years, with the addition of grit of various sizes, vermiculite, perlite and cat litter (expanded clay). The properties of the coir have varied; early examples being much more "rough cut" than the material I get from my current supplier. I was finding quite large pieces of unmilled coir in the mix, which was not good when potting small plants & seedlings. My current material is quite finely milled, with some hair-like fibres included. I get good results from using this mix but it is essential to fertilize regularly as coir doesn't retain nutrients.

[fanaticactus]

I've used coir exclusively as the main constituent of my cactus & succulent compost for the past three years, with the addition of grit of various sizes, vermiculite, perlite and cat litter (expanded clay). The properties of the coir have varied; early examples being much more "rough cut" than the material I get from my current supplier. I was finding quite large pieces of unmilled coir in the mix, which was not good when potting small plants & seedlings. My current material is quite finely milled, with some hair-like fibres included. I get good results from using this mix but it is essential to fertilize regularly as coir doesn't retain nutrients.

Thank you, sir, for this information. Your description sounds exactly like the coir I have. And fertilizing will henceforth be uppermost in my mind!