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Organic Gardening: Use of coir in cactus mix

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Forum: Organic GardeningReplies: 4, Views: 62
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San Dimas, CA

May 25, 2012
2:15 PM

Post #9138449

I keep reading about the advantages of using coir (coconut fiber) as a replacement to peat when creating a cactus mix. I cannot find coir locally (it is sold as a compressed brick) but I do see coconut fiber liners which are used for hanging baskets. I was thinking of just buying a couple of these liners, mashing them up, and using them in my cactus mix - will this work?


Bay City, MI
(Zone 6a)

May 25, 2012
7:02 PM

Post #9138801

What are the advantages you're reading about? The most significant advantage is coir is easier to rewet after moisture levels slip much below 30%, and that really much of an advantage because most good cacti mixes have very little coir OR peat because the small particle size of either/both supports too much water retention.

What I use for cacti & succulents:


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San Dimas, CA

May 26, 2012
11:42 AM

Post #9139427

Thanks for the response. I read that coir was better than for the reasons you stated. Also coir takes longer to decompose than peat, and is PH neutral rather than acidic like peat. I also read most commercial cactus mix isn't the best for the plants. I would like to know what you use in your mix? Your plants appear to be doing quite well.


Bay City, MI
(Zone 6a)

May 26, 2012
12:20 PM

Post #9139461

Peat and coir break down at about the same rate, with peat getting a slight nod as slightly more stable. Their water retention curves are very similar. Neutral pH isn't something you would consider desirable for container media. Where a pH of 6.2 might be considered ideal for mineral soils (gardens), a full point lower, 5.2, is closer to ideal for container media, so using large fractions of coir in container media precludes the use of dolomite as a liming agent, lest you end up with a pH so high it renders many or most of the micro-nutrients unavailable. Coir also has a very high K content, which needs to be considered and allowed for in your fertilizer regimen or the excess K can cause problems with the uptake of P, Ca, or Z.

I use a mix of

1 part screened Turface MVP
1 part screened pine or fir bark
1 part grower grit (crushed granite) or #2 cherrystone (quartzite)

It's the most productive soil I've ever grown in, as well as the easiest and most forgiving. I have (literally) hundreds of long term planting in the soil pictured. Read more about it and learn why, here:



Everett, WA
(Zone 8a)

May 30, 2012
6:55 PM

Post #9145444

Hmm! I see from Google that "#2 traction grit" is called 3/16", or almost 5 mm. Pretty coarse! Nice.

(I'm going to add that to my litany of "do you have any ..." when I go shopping for affordab le soil amendments.
I've found crushed rock in semi-random sizes, and "#2 chicken grit - crushed granite". I would have said the #2 chicken grit was closer to 1/8" or 3 mm.

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