Sand

[Paul Tyerman]

Ray,

If you were to actually put a layer of sand under normal soil the water
would actually sit on top of the sand.  It sounds crazy but it is actually
the truth.  It has to do with the density of the particles and water not
wanting to move from a higher density (soil) into a lower density (sand) or
something like that.

Effectively the top of the layer of sand (or actually the bottom of the
layer of soil on top) would function a bit like the bottom of a pot.  No
matter how many drainage holes you have in the bottom of a pot, there will
always be a water sitting in the media at the bottom of the pot as it won't
drain out of hte soil into the open air (the ultimate in lower density
<grin>).

Mixing the sand in with the soil adds to drainage by decreasing density and
increasing the size of air pores, but putting a layer of sand in would
actually produce a mini "water table" sitting just above it which (if the
tuber is sitting in it) could be catastrophic from a rot point of view.

This year I purchased an Eranthis (I realise that this isn't an aroid, but
it is just to serve as an example) which I have tried twice before and lost
to rot both times before it acclimatised.  I potted it in a pot with normal
potting mix, but put the corm effectively into a "pocket" of sand.  By
putting it into the pocket of sand the water tended to go around it, rather
than entering the sand (using the water table mentioned above to advantage
instead of disadvantage) as the density of the soil was greater than the
sand.  There is still enough moisture entering into the sand during
watering, but it drains very quickly out of there (from less density into a
higher density) while it percolates more slowly through the soil.  The
roots of the Eranthis headed out from their sand pocket and into the soil,
but the corm itself was kept relatively dry and rot-free.  The shoot is
just poking its little head above the surface now.  Yippee!!!! (You have no
idea how pleased I am to finally get one of these damn things to survive
<big grin>)

Does that all make sense or have I confused you more?  If I can clarify
anything please let me try <grin>.


Cheers.

Paul Tyerman
Canberra, Australia.  USDA equivalent - Zone 8
mailto:ptyerman at ozemail.com.au

Growing.... Galanthus, Erythroniums, Fritillarias, Lilium, Aroids, Irises
plus just about anything else that doesn't move!!!!!