In article ,
Mike Lyle wrote:

[ Ivy ]

If you're moderately brutal, twice a year; if you're really brutal,
once. Unless you're artistic about it, it will look horrible for
amonth or two afterwards. But you cannot afford to forget twice
running.

Oh, I don't know - just get out your machete and get stuck in! All
right, it will take a year or two to look good again.

On the matter of USDA-style zones, deprecated by Nick, the problem
with the British Isles is that they are relatively small areas of
extremely varied relief stuck in the North Atlantic: within them you
can find climates varying from, let's say, Maine to maybe North
Carolina to Oregon within a bus-ride. I recognize the map you refer
to as very much the same as what's in the standard agricultural
textbooks; but the trouble is, it only takes a hill, or a row of
houses, or even a wall to change the picture completely. It's
endlessly fascinating; but I can see why the Brits invented the US:
so much simpler!

Even worse, our two main clines have very little to do with the
lowest winter temperatures. While there IS a correlation between
those and the north/south sunshine levels, it is pretty misleading
when applied to the inhabited areas (which are increasingly maritime
as you go north). And the problem of waterlogging is correlated
more with soil than climate, though it has some correlation with
the west/east rainfall cline.

However, to refer to your USA examples - sorry, no. It's nothing
like that, I am afraid. Our variation is only Vancouver to Anchorage,
and we have nothing like those locations you mention. The reason
that USDA zones work there is that most of the main clines are very
strongly correlated, combined with the fact that the main cause of
winter tenderness IS the lowest winter temperature.

We could just about use their zones, provided that we don't assume
that USA "zone 8" plants are UK "zone 8" ones, but it would still be
pretty unreliable. That isn't how things work here.


Regards,
Nick Maclaren.