Perched Water Table

Peter Taggart
Wed, 04 Dec 2013 09:42:57 PST
Tall or short, a pot of compost without a capillary link to the ground or
to a capillary mat of some kind, will always have a soggy bit at the bottom
after watering -unless the water is very limited. A taller one will have
more drained volume at the top. This is a good reason to use a sand bed or
plunge to sit the pots in. It is also one of the reasons why I use a lot of
clay pots.

Provided that there is a capillary link to the bottom of the pot the water
can travel down there, (and out of the pot if it is not crocked and the
compost touches the surface on which it is stood), irrespective of light
weight objects in the mix.
I suggest that the recipe for a large container with the bottom filled with
empty cans or plastic bottles is good, but with the modification that there
be no membrane, and that the cans be stacked vertically in order that the
compost percolate between them, down to the drainage holes, and provide a
link to the surface on which the pot is stood.

On Wed, Dec 4, 2013 at 4:58 PM, Chad Schroter <>wrote:

> SO if you want to maintain drainage and save weight you must use a
> material of the same particle size - but lighter.  Perhaps the Styrofoam
> beads used in "bean bag" chairs would work better than Ghost Farts.
> -----Original Message-----
> From: []
> On Behalf Of J.E. Shields
> Sent: Wednesday, December 04, 2013 8:45 AM
> To: Pacific Bulb Society
> Subject: Re: [pbs] Perched Water Table
> The problem is capillary action holding water in the fine spaces in
> the medium.  Until the hydrostatic pressure of the vertical column of
> water exceeds the capillary attraction/surface tension of the water
> at the bottom of the medium, the water won't flow down and out.
> You will always get a better draining bed when the medium is uniform
> from top to bottom.   In addition, the taller the water column, the
> better the top of the bed will be drained.  It's physical chemistry
> or physics at its finest.
> Jim Shields
> At 08:40 AM 12/4/2013, you wrote:
> >Agreed that if the thought is that crocking results in better drainage -
> >well, that's a crock of animal fertilizer.

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