Broadback wrote:
A large area of my garden has no appreciable top soil. I have
started
digging out a large bed, which I will fill with top soil. How
deep,
ideally, should top soil be?
TIA

The length of a piece of string is generally sufficient. Or, to put
it more helpfully, it depends what you want to grow. I'd say that for
practically anything, with "average" subsoil consistency, a spade's
depth should do you most handsomely. An awful lot of garden plants
will do fine on a fraction of that, especially if you can dig in some
organic material underneath (I wouldn't even bother to wait till the
stuff had rotted if I were in a hurry, but I know it's against the
rules). I've grown good ericas in a horrible mixture of subsoil and
stones, and other things with what amounted to only a three-inch
layer of reasonable soil and gone-off silage pricked in on top of
stony clay. There's no soil so bad that it can't be turned into good
soil.

--
Mike.