I know this is a year old thread but I think you might be right about the wind. I have Dew Drop, Summer Blood Birne, Flemish Beauty, and Aurora in my greenhouse. As I have said many times before it is in zone 2, a plastic hoop house and unheated in the winter. Minus 30C sometimes for weeks and -40C for as long as a week at a time. They have zero tip dieback I have not had to trim dead branches off and these trees are not covered.
That said, the Dew Drop is on contoneaster roots and is going to have lots of blossoms this spring, the others have not blossomed yet. So although they live well I am not sure if the cold kills the buds, or if they are not old enough.
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