On Mon, 07 Jun 2010 08:57:04 +0100, Chris J Dixon
wrote:

Having just extended a flower bed to incorporate what has been
lawn for 40 years, I am left with some pretty solid clay soil.

Gypsum is recommended as a soil improver, but appears to be sold
in garden centres as a proprietary product costing nearly £5 for
2.5 kg.

http://www.capitalgardens.co.uk/clay...er-p-6321.html

On the other hand, I can pick up a 25 kg bag of multi-finish
plaster for under £5, and AFAIK this is essentially the same
material.

Any reasons not to go with plaster?

Chris

30 - 40 years ago there was a product sold and given much publicity,
called Acta-Bacta. It was supposed to break down clay soil and I
think that contained gypsum. I tried one sack. It made no
difference!

Pam in Bristol