From: "Derek Burch" derek at horticulturist.com> on 2002.10.27 at 13:39:20(9585)
Mike, we very often answer this sort of question by going back to what the
roots do for a plant (bring in water and dissolved minerals and hold the
plant steady so that its leaves can be in the light). Then you can consider
the question of what the roots must have as living parts of the plant, which
points out the need for available water and dissolved materials and the
opportunity for exchange of gases (oxygen in and carbon dioxide out).
Now, how can we do in a pot what the plant finds in its natural habitat with
respect to where its roots sit? The answer is that we can scarcely do it
perfectly, but can make a stab at giving the source of liquids and the
aeration (and the support) by getting the watering correct for whatever mix
we choose. And I say that deliberately because I think that it is possible
to grow in almost any medium - the trick is to find one that you can water
easily and correctly, get thoroughly familiar with that and stay with that
for most of your plants. Be willing to change if certain ones are not doing
well, and in order to do this sensibly, understand a little about the
components and whether each will give better aeration or better water
holding or both, and so on.
Deni's mix would be too heavy (read not enough air space) for my style of
watering, which has been strongly affected by working with the soilless
mixes common in Florida nurseries. I would start to build from good quality
peat moss and very coarse sand (try sandblasing sand). Perlite will do some
of things that sand will, but stay away from vermiculite since it is
shortlived in the form in which you would incorporate it. Coir is being
offered as a peat moss substitute - it doesn't work for me, but I did not
give it a fair trial by adjusting my watering as I should have.
Now this is starting to ramble - perhaps you would like to go to my website
for a little more.
The internet, of course, is full of information, far too much to hunt
through, so my simplistic approach may be some help. Derek