Searching the archives + What Do You Think Of Coconut Coir?
Roy Herold (Wed, 28 Jul 2010 14:57:09 PDT)

I had a terrible, terrible experience with coir from which I never
really recovered. I was using some of the compressed brick types that
are sold by many outfits, but mine came from a local plant society that
claimed 'wonderful' results. According to recommendations, after
hydrating I mixed it with grit or pumice or perlite, whichever seemed
most suitable.

About a quarter of what I planted in it, mainly bulbs, succulents, and
some general perennials, died within a year. Half went into near stasis,
and just sat there, putting on no new growth, no new roots, complete
zombies. The other quarter seemed happy as could be. Cyclamen
rohlfsianum absolutely loved it, and grew into monsters. Narcissus
absolutely hated it, and I lost most of my collection.

In the subsequent repotting effort I threw buckets and buckets of the
spent coir in a big heap by the compost pile. This heap was completely
weed free for a couple of years, as if it was saturated with herbicide.
The ground around it was weedy as ever, right up to the invisible coir
barrier.

That said, I still use coir. I did more research and found that orchid
folks who use it have a long and involved regimen of rinsing and soaking
and rinsing and rinsing and treating with epsom salts, ad infinitum.
Apparently the coconut hulls come from some very salty locations, and
the processors do not wash it. The rinsing regimen is not for me, thank
you. Instead I switched over to MetroMix with coir (don't remember the
exact number, but I like the one without vermiculite). I still mix this
with grit or pumice or perlite. They do all the washing for you, most
certainly test it, and pretty much have to guarantee performance or they
will have a lot of BIG angry customers.

Or, if you want to live dangerously, use the raw stuff and you may find
you will soon have a lot more room in the greenhouse like I did.

--Roy
NW of Boston