"stuart noble" wrote ...

, AL_n wrote:
I'm planning to make some self-watering planters, using a bed of water-
absorbent granules (vermuculite would work). I will then cover the bed of
granules with a synthetic filtering membrane and drill some overflow
holes
just below the top surface of the granule bed. I will then add a filler
tube going down into the bed of granules, before filling the container
with
compost, and planting.

The granules could be corse vermiculite. I wondered if anyone can suggest
an alternative material that is less expensive? Broken up building blocks
(the aerated lightweight type) might be one option. Anything absorbent
that
doesn't cantain harmful minerals or chemicals and is non-perishable might
work.



Try Rockwool. Ridiculously cheap at B&Q. You may need to prevent the
insulation becoming compressed by the soil.


I understand Rockwool comes in two types, water absorbent and the opposite.
I know a chap out Hampshire way that was experimenting with it many years
ago for growing orchids and similar and was using both types together to
provide both air and moisture to the roots.
On thinking about it, that is where a specialist book of mine I've been
looking for went, he borrowed it and moved.
--
Regards. Bob Hobden.
Posted to this Newsgroup from the W of London, UK