In article ,
says...
David in Normandy wrote:
In article .com,
says...
I wonder if anyone has an opinion about the water retention of sand
when mixed with the general purpose compost you buy in a garden
centre. My experience is that, added at 25%, the mix actually retains
more water than the compost alone. Maybe this is partly due to the
sand breaking down the compost into fine and evenly distributed
particles or something.
Any thoughts welcome


I almost always mix around 20% of sharp sand with multi-purpose compost,
the plants / cuttings / seeds / seedlings all seem to fare better than
with just plain compost. It doesn't tend to shrink so badly and like you
say it's water retention properties seem a bit more "balanced" allowing
excess to water to drain through but holding moisture for longer.

The most noticeable effect is with cuttings, they much prefer some sharp
sand mixed in.

I've wondered about soft sand too. It should work in the same way but I
suppose wouldn't break down the compost as easily when you mix it. Nice
fine structure though.

The only concern I have with sand is making the texture attractive to
ants, which have killed off a good few of my window boxes over the years.

Personally i would avoid soft sand/builders sand as this often has a
percentage of clay and its action in compost is not what you would expect
and you will get a lot of rotting problems it can also contain lime
(which sharp sand and horticultural grit should not)
--
Charlie Pridham, Gardening in Cornwall
www.roselandhouse.co.uk
Holders of national collections of Clematis viticella cultivars and
Lapageria rosea