The winter of 1995-96 will be remembered as the coldest winter on record in Minnesota. The all-time state low minimum temperature of -60° F was recorded at Tower, MN on February 2, 1996. While the official low temperature at Grand Rapids was 41°F, we observed -53°F in our strawberry plot area and other reports in the -50 to -55°F range were common in the Grand Rapids area. Temperatures of -40°F or less were recorded on nine dates in our blueberry and strawberry plots during the 1995- 96 winter. At the same time northern Minnesota received above average snowfall in January and February that protected herbaceous perennials, strawberries and blueberry plants from the record cold temperatures. Blueberry plots, in fact produced record yields in 1996 despite the record cold because of the deep snow.
In contrast, exposed plant tissue suffered much winter damage. Nowhere was winter damage due to the record cold more evident than to fruit trees. In our orchard many trees were totally winter killed and almost all trees suffered some winter injury. I had many calls from people who lost trees or had trees badly damaged. Fruit production in our orchard that had reached an all time high during the 1994 and 1995 growing seasons was the lowest it had been in many years. Periodically 'test winters' provide a severe cold test for tree fruits and the winter of 1995-96 resulted in the worst winterkill I have witnessed in over 25 years. It truly was a 'test winter'!
While no one likes to see such severe tree death and damage, one of the values of the North Central Experiment Station is as a cold winter hardiness testing location and the winter of 1995-96 provided us an opportunity to evaluate apple cultivar hardiness. The table lists the relative survival of the cultivars in our orchard following the 1995-96 winter. Winter damage was worse on the so called "hardy" cultivars than would have been predicted. Anything in the best survival list should be considered very hardy and dependable for nearly any winters we may have in northern Minnesota. The intermediate list contains many cultivars we normally think of as being "hardy" and probably would survive most winters in northern Minnesota. Even some of the cultivars in the worst survival list have produced well in our orchard. Many of these trees were over 10 years old. There were a few things in the survival that should be noted that reinforced ideas we have already known. First, crabapples are much hardier than large fruited apples. Among the best survivors were: Rescue, Dolgo, Chestnut, Whitney and Centennial Crabs. All except Dolgo are good eating crabs. Second, some of die old varieties of Russian origin are very hardy. Cultivars like Charlamoff, Antonovka and Hibernal have long been considered very hardy and were used by old time orchardists as hardy framework trees years ago. If they only tasted good! Third, dwarf trees survived as well as standard trees. Trees died because of top damage. Most trees with dead tops had a root system that survived. Many root systems sent up shoots showing that the dwarf root system survived where the top died. Fourth, several McIntosh types are not hardy enough for most northern Minnesota locations. These include Britimac, Spartan, Killand, McLemore and Quinte. Lobo appears to be the hardiest McIntosh type.
There were a couple of surprises in the survival patterns. The most surprising survivor was Honeycrisp. This new U of M release came through the winter well. While it would be great news if this fine quality apple exhibited superior hardiness, the trees are young and we need additional evaluation on them to say it truly is hardy. Perhaps the biggest disappointment was Mantet. Normally considered very hardy it suffered severe winter damage in two places in our orchard.
The ranking of the remaining cultivars in the list pretty accurately describes their relative hardiness based on survival from previous evaluations at our location. The survival ratings in the list should be considered the worst case scenario for winter hardiness damage. Then too, the winter of 1995-96 was the coldest on record and hopefully will not be repeated for many years.
If any of you have observations from your own fruit tree survival, write me a brief note. I'll report any significant findings in a future North Central Quarterly article.
Best Survival: Rescue Crab, Dolgo Crab, MN 447, Chariamoff, Chestnut Crab, Whitney Crab, Folwell, ?Honeycrisp?, Garland, Centennial Crab, Carrol, Wellington.