Pam Moore wrote:
Leave it as long as possible but watch it carefully. In my experience
the tops die down very quickly and unless you lift it before they do,
you won't know where they are, unless you've marked them very exactly.
I often find stray garlic coming up in Spring because I'd forgotten to
lift it.

Heh, I found it very exciting digging up a row of 'forgotten' garlic a few
years backk. "Look, another one!!" all day long. :-) (I think I'd given
up on the patch cos the onions all got white rot, but the garlic survived
but died back, so I thought it had gone)

My garlic this year is ropey. :-( Lost most of it, presumably due to lack
of water. One day it was there, couple of days later went back and it's all
died off and there are some rotten cloves lying around. Still got some
going strong on the boys' bed (I really ought to stop stealing their raised
bed - but it's the only decent patch that is always available in an
emergency for transplanting into!!), but it doesn't seem to have split into
cloves yet, which is weird, cos it's certainly ha a cold spell!