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.

Al

On 04/07/2012 09:16 PM, 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.

Yes, you can use cat litter if you find the right kind. What used to be
sold as "Tesco's Premium", I think it's now "Tesco Dust Free", is
produced as a horticultural additive, but sold for many times the price.

I use a cheap cat litter made from sepiolite, which works really well.
I have run an experiment over several years and it doesn't seem to break
down at all.

Generally recommended is diatomaceous earth, I think you want to avoid
clumping litters like Fuller's earth.

Here's a link that discusses it in the bonsai context. I don't do
bonsai, and it works just as well.

http://www.bonsai4me.com/Basics/Basicscatlitter.htm

HTH

On 07/04/2012 20:16, 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.

Al

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

http://www.diy.com/nav/build/insulat...ation-12057529

stuart noble wrote in news:XRdgr.32840
:


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

Thanks; your suggestion gave me another idea: polyurethane foam, as used in
Celotex wall board, etc. I seem to recall that it absorbs water like a
sponge, but doesn't compress significantly.

Al

Emery Davis wrote in
:

I use a cheap cat litter made from sepiolite, which works really well.
I have run an experiment over several years and it doesn't seem to
break down at all.

Generally recommended is diatomaceous earth, I think you want to avoid
clumping litters like Fuller's earth.

Here's a link that discusses it in the bonsai context. I don't do
bonsai, and it works just as well.

http://www.bonsai4me.com/Basics/Basicscatlitter.htm


It sounds like a possible option. Thanks!

Al

On 08/04/2012 12:57, AL_n wrote:
stuart wrote in news:XRdgr.32840
:


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

Thanks; your suggestion gave me another idea: polyurethane foam, as used in
Celotex wall board, etc. I seem to recall that it absorbs water like a
sponge, but doesn't compress significantly.

Al

I think you'll find Celotex is closed cell foam which absorbs no
moisture at all :-)
Loft insulation is basically the same stuff as the Rockwool plugs used
in hydroponics. I've used it as a base in hanging baskets but, unless
very well concealed, the tits will take it away for nest building

stuart noble wrote in
:

On 08/04/2012 12:57, AL_n wrote:
stuart wrote in news:XRdgr.32840
:


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

Thanks; your suggestion gave me another idea: polyurethane foam, as
used in Celotex wall board, etc. I seem to recall that it absorbs
water like a sponge, but doesn't compress significantly.

Al

I think you'll find Celotex is closed cell foam which absorbs no
moisture at all :-)

I see. It must be the open-cell pulyurethane foam that I was thinking of.

Loft insulation is basically the same stuff as the Rockwool plugs used
in hydroponics. I've used it as a base in hanging baskets but, unless
very well concealed, the tits will take it away for nest building.

Thanks for the suggestion, but I think the compressible nature of rockwool
poses a problem for my purposes, at least for the type of lef-watering
system I'm envisaging.

Al

"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

On 08/04/2012 17:47, Bob Hobden wrote:
"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.

Rockwool holds moisture but doesn't absorb it (if that makes any sense).
A J cloth works in a similar way, as do microfibre cloths etc.

stuart noble wrote in news:Qblgr.68233
:

Rockwool holds moisture but doesn't absorb it (if that makes any sense).
A J cloth works in a similar way, as do microfibre cloths etc.

Certainly rockwool holds water after it has become drenched. However, if
you were to half-submerged a wad of it in a pot of water, would the
unsubmerged part soon become wet too, say by capillary action, (in the way
some high-absorbent synthetic mops do)?

Al

On 10/04/2012 11:54, AL_n wrote:
stuart wrote in news:Qblgr.68233
:

Rockwool holds moisture but doesn't absorb it (if that makes any sense).
A J cloth works in a similar way, as do microfibre cloths etc.

Certainly rockwool holds water after it has become drenched. However, if
you were to half-submerged a wad of it in a pot of water, would the
unsubmerged part soon become wet too, say by capillary action, (in the way
some high-absorbent synthetic mops do)?

Al

Dunno. It's full of air (like supermarket bread), so I suppose it might
float initially.
ISTR there is no capillary action with a JCloth i.e. only the bit in the
water gets wet. In fact, I've never been able to demonstrate wicking to
my own satisfaction.

On Apr 7, 8:16*pm, "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.

Al

Compost also holds water... do these granules really achieve much?


NT

On 10/04/2012 21:04, NT wrote:
On Apr 7, 8:16 pm, 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.

Al

Compost also holds water... do these granules really achieve much?


NT

They hold an awful lot more water than soil or compost but IME, once
they're allowed to dry out, they're finished. When I've used them for a
season I've never seen any trace of them the following year, so I guess
they degrade quite quickly.

This is interesting
http://www.puyallup.wsu.edu/~linda%2.../hydrogels.pdf

I prefer vermiculite, which IME permanently increases the soil's water
retention.