Throwing in the Towel
> From: zbigniew at netcom_com (Patrick Farley)
> What I'm interested in is a good substrate composition? What is laterite
> and should I use it? How about peat? Gravel? Children's sandbox sand?
Your question will generate many and varied responses :-)
I have been very happy with quartz sandblasting gravel with a grain
size of about 1/16". Fine enough so that plants can anchor well and
coarse enough so that water flow is not severely restricted. In the
Denver area, most of the stores sell this stuff (called "TexBlast") in
50# bags for $9.50.
Laterite is highly weathered, iron bearing volcanic soil. The most
reliable (and expensive) source is Dupla. A small amount (a pound or
so) is mixed in with the lower 1/3 of the gravel. This provides a lot
of initial iron and is able to chelate nutrients if there is some
water flow through the substrate.
I wouldn't recommend peat since it may decompose and cause trouble,
but others will swear by it. It serves the same chelating purpose as
laterite but does not provide iron.
Coarser gravel is not good because the roots can't anchor the plants
as well and detritus will fall between the grains and become trapped
in the substrate. Sand is too fine since it blocks water flow and
prevents nutrients from getting down to the roots.
Your results will vary.