North American Fruit Explorers mailing list at ibiblio

[Bernie Nikolai <BNikolai@shaw.ca>]

Both Honeycrisp and Zestar are outstanding tasting cultivars from the
University of Minnesota's breeding program.  I have been testing both for
over 10 years, to see how they would do in my harsh zone 3 Canadian climate
in central Alberta.  While not scientific tests, my results are pretty
accurate for folks wanting to grow these excellent apples in cold climates.

In a nutshell, both Honeycrisp and Zestar seem equally hardy for me over the
last 10 or so years.  As a comparison, both are hardier than McIntosh, a
variety that is normally considered quite hardy, but for me, only exists in
near perfect microclimates in the city of Edmonton, and won't exist at all
outside of the city.
    The rootstocks I have used under these cultivars are Siberian Crab,
Ranetka Crab, V1, V2, Ottawa 3, M26 and Bud 490.  I wanted to see if any
rootstock combination worked to impart extra hardiness (unfortunately, none
did from what I could see over the last 10 years).  Here are the results for
both cultivars:

to -37.5 or -35F no damage
-37.5C to -40C or -40F - tip dieback in the spring, between zero to 24
inches, once the temperature reaches -37.5C or     -35F.  The closer the
temperature dips to    -40C  the  more dieback you get.
-40C and colder - complete dieback of the entire tree to the snowline.

The coldest I have recorded at my orchard site is -43C, or about -45F, and I
have been experimenting with about 36 Honeycrisp and Zestar trees.  As a
matter of interest the only commercial apple that has withstood these
temperatures and produced without significant dieback is Wealthy.  But the
production of Wealthy has been light for me.

The best apple I can grow in my opinion is a test variety from the
University of Saskatchewan, "18-10-32".  I understand this will probably be
released this spring under the name "Sweet Sunsation" or just "Sunsation".
This is a large firm  apple , yellow with a beautiful red blush on the sunny
side, that is delicious in fresh  taste  (tart/sweet) and is truly
outstanding for pies.  It took -43C without even the slightest hint of tip
damage, and produced bountifully the next year on all trees.  It also stores
well into the new year.
Bernie Nikolai
Edmonton, Alberta
zone 3/2