Alan Holmes wrote:

(snip)

And it is not true that the zone system should only be valid for a
specific group of plants. How could it? It just gives the "average
annual minimum temperatures" for any spot in the world. Of course, it
is true that it was developed and first used for commercial crops in
the US.
I fully agree (as you will see, if you look at the first answer that
was given in this thread) that there are many other factors, which
also influence a plant's survival. But a serious gardener should be
aware of those factors, not close his mind to some of them.
But then, all this has been said before...

For some inexplicable reason you americans seem to overlook the
fact that we do not have 'Zones' we have 'weather'!

Alan

Sorry, Alan, I'm not American :-)
But - I wonder if you really think there's no zone difference between
the Isles of Scilly and the top of Ben Nevis... :-))

Regards,
Roger.