On 05/02/2019 10:49, Another John wrote:
A chap I do a bit of gardening for had a couple of his borders flooded
last year by a change in subterranean water flow. That has been fixed,
but the borders are still "sticky".

He wants to dig sand into the borders. Fine, but he has specified
"horticultural sand". I think it would save him money if I just used
ordinary sharp (concreting) sand from a builder's merchant. What does
the team think?

Sand is hard work and the worms are not so keen to work it in for you.

Spent mushroom compost or horticultural compost from a garden centre
that really grows plants for sale (as opposed to importing them) are the
best cheap options for stuff to lighten the soil. You can sort of get
away with a rough mulch after just breaking up the clay into spade sized
lumps as well since worms and weather will mix it up for you eventually.

You want a sharp grit sand if the aim is to improve drainage. Building
sand tends to have a bit too much fines in it (which is great for making
concrete and mortar set but not ideal in a clay soil).

--
Regards,
Martin Brown