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<pre>Dear antonio and others.

The critical climatic parameter for the olive is temperature. If it is
below zero degrees Celcius there is increased likelihood of frost
damage. If it is above 35 C and especially greater than 40C pollination
is impaired. A number of chill hours are required for fruiting.
Flowerbud initiation commences in summer (at the molecular level). In
winter the flower buds are released from dormancy (bud break)after the
olive experiences a certain number of chill hours (Day length may also
play a roll). Different varieties require differing amounts of chill
hours. For example Sevillano requre 4-5 times the chill hours of
Kalamata and Koroneiki. At bud break, the bud from which flowers will
ultimately develop, and shoots recommence growth in Spring as the
temperature increases. You can see the buds differentiating into
infloresences with flower buds developing. The flowerbuds swell, petals
form and flowers open. Flowers are wind pollinated and to a lesser
extent insect pollinated. Once flowers are fertilised fruit development
occurs. As a rule of thumb most varieties will flower and fruit if the
Average monthly winter temperature (eg Southern Hemisphere = July
Northern Hemisphere = December) is between 10-12C. For example the olive
true grows well in tropical countries but does not flower because of a
lack of chill factor. Much of the reserach for chilling etc has eminated
from USA, Spain. Italy and Greece. Professor Andrea Fabbri from the
University of Parma is a specialist in this area and he is currently
experimenting with olive growing under ultra cold conditions. He is a
One List subscriber and I am sure he can add further comment.

Prof Stan Kailis
Perth WA

Regarding water the minimum annual requirement for a mature tree is the
equivalent of about 250 mm rainfall. mature olive trees receiving 850
-1000mm of rainfall mainly in winter do not require irrigation although
average yield may be reduced and alternative year fruiting patterns are
more pronounced.

For Arizona. Can you please send me the names of some major centers and
I will check out the climatic conditions and olive growing for you.

Prof Stan Kailis.
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