Re: SV: Growing appples in a Mediterranean Climate

Dear Gunnar, 

I wrote you the following message a couple of days ago and it would not send--some malfunction of my internet service provider. I couldn't even save a draft in my e-mail system, but saved it to a disk and have copied it below for you to see. It reiterates what Carol said about the chill factor. Perhaps the most important additonal information is that the chill requirements for each variety are carried in scionwood of that variety. Here is my previous message:

Dear Gunnar,

The main question, when growing deciduous fruit in a mediterranean climate is: what is the winter chill requirement of the fruit variety. Apples, pears, apricots, etc. require a minimum amount of winter chill, which is calculated usually in hours above 32 degrees F but below 45 degrees F. A particular type of fruit will have varieties that require more chill and ones that require less chill. If the tree (or the grafted branch) doesn't receive enough hours of chill to meet its particular requirements, it may not bloom, or will bloom late and sporadically, often not having enough blossoms open at once to achieve pollination or cross pollination. 

Mediterranean climates vary considerably in the amount of winter chill they provide. Just within the San Francisco Bay Area, in California, we range from 100 to 900 degree hours per winter. In urban areas, the exact number of hours is harder to find out, but in agricultural areas, it is often made available to farmers. So if you are in a city, but can compare your local climate to a nearby agricultural area, you may be able to get a good idea of what you have.

Apple varieties range in the number of hours of winter chill they need from as many as 1,800 chilling hours to as little as 200 chilling hours. It is entirely possible that the varieties you brought from Scandinavia have a higher chill requirement than the one your Greek climate can provide. If you know what varieties you brought, you can look up their chill requirement in a mailorder catalog that sells them or in reference books. 

Once you know how many chilling hours you have in an average year in your location, you can look for the appropriate apple varieties to grow where you are. The ones that take very very little chill, such as 'Anna' (200 hours) and 'Winter Banana' (400 or less hours), or 'Beverly Hills' (300 hours) are, in my opinion, not very good. They aren't firm enough for my taste. (But maybe a new low chill variety has hit the market since I did my last research.) For areas with at least 600 chilling hours, some possibilities are 'Braeburn', 'Granny Smith', 'Gravenstein', 'McIntosh', 'Mitsu', 'Red Astrachan', or 'Pink Pearl'. (All but 'Braeburn' and 'Granny Smith' need a pollinator of a different variety.) Or look locally for varieties that are sold to succeed in your area. (Maybe other Medit-garden group correspondants have other favorites?)

The fact that the branches are grafted should not be a problem if the grafts are all varieties that have a similar chill requirement and one that can be met by your local winters. If their chill requirements are too dissimilar, even if they are all met by your climate, they will flower at different times, precluding cross pollination, and reducing the chances for pollination at all. It also tends to exhaust a fruit tree to bloom over a long period of time due to insufficient chill overall or to grafted branches that are blooming at different times. 

Pears require, on average, about 600 hours of chill. For areas with less than 600 hours of chill, there are 'Comice' (200-300 hours) (self-fruitful), 'Moonglow' (500-700 hours) (needs a pollinator), and 'Seckel' (500 hours) (self-fruitful). 

Hope you have success getting fruit in your garden. 

Best wishes,

Pam Peirce
San Francisco, CA
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