Date: Thu, 24 Apr 1997 11:19:18 -0700 From: Wim Leys <wim.leys@lin.vlaanderen.be> To: cp@opus.hpl.hp.com Message-Id: <aabcdefg1636$foo@default> Subject: Re: perlite, vermiculite?
Hi Niels,
> I have an English dictionary but perlite and vermiculite are not there.
> Could someone explain to me what it is. I understand that it is used for
> making soil with good drainage.
Perlite is expanded alunminiumsilicate, it looks like white grains, has
the porosity and appearance of tuffa-rock (the pebbles you can sometimes
find in "stone-washed" jeans) but is not so hard. Given enough pressure,
you can pulverise it between your fingers.
What vermiculite exactly is, I don't know, but it looks like expanded
mica. It looks beige and glitters a bit. It is soft like expanded
polystyrene ("isomo") and it can as easily be compressed between your
fingers.
I stopped using vermiculite. My plants (Sarr, VFT, Nep, Darl, Dros) just
don't grew well in it.
Perlite on the other hand is excellent for making a light and well
drained soil mixture. It can however not replace coarse sand. Peat tends
to compact after a while, sand prevents this from happening, the added
perlite improves the structure and the drainage capacity.
Before using perlite you can soak it for a while in water, otherwise it
will float when you place the pots in water. I keep a barrel constanly
filled with perlite and water, so whenever it's needed, it's already
soaked.
> I use some light expanded stuff called
> "leca" in Danish. It is brown on the surface and black inside. Is it the
> same as perlite or vermiculite, you think?
Perhaps this is expanded clay (in Belgium it is sold as "Argex" grains).
It can be used at the botom of pots to prevent roots from constanly
standing in water. It can be used for Darlingtonia and Heliamphora.
Kind regards
Wim
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