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<pre>NEVILLE BURT


Dear Neville,
I don't know NZ well. In fact the only part I know is
Blenheim. There does seem to be a major differenence in the cold here
compared to NZ. The winter cold that does the damage is the Tramontana.
That is when some Artic or Siberian air spills down south over the Alps. It
means sub zero temperatures day and night for a few days and the damage
occurs when it goes down to - 7 or -8°C We get winter ground frosts as well
which can be quite cold (we have not recorded as low as that but our
thermometer is near the house on the top of the hill and the ground frosts
in the valley could be more severe) but we have not recorded any damage
from them.

We have had one frost in spring over the last ten years that caused
damage. I don't know the temperature as we were away at the time but when
we got back we found the walnuts below the olives in the bottom of the
valley were scorched and the young olive trees were burn on the tips. There
seemed to be little damage to the older trees and the crop was normal.

Last year was our coldest harvest with an early Tramontana and snow
(it did not settle) but the temperature was still just above freezing.

In NZ or at least in Blenheim they seem to have a number of ground
frosts but no equivalent of our Tramontana as the Antartic air does not
reach NZ at sub zero temperatures. The frosts can be severe but only for
short periods at night. I doubt they would do much damage even if they
reached -8° but I am only guessing.

One useful idea passed on to me by Richard Bowling who is a
vineyard consultant near Blenheim is to look for local indicator plants
that have a similar frost tolerance to olives. He has done this with
terrific results for vines in the Marlborough area. Brilliant work!

With our big frost in the winter of 1996 the oleanda plants were
more severely frosted than the olives. We have no eucalypts but nearby some
lemon scented gums were completely burnt off. Rosemary seemed more
resistant with only tips being burnt.

There is a wide variation in frost tolerance between varieties.
This is listed in the standard text books but if things are really frosty
try some varieties from Mt Amiata in Tuscany or Nocera in Umbria.

Cheers Brian Chatterton.
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