i know it isn’t the answer you are looking for, and admittedly isn’t helpful to your current situation, but the ultimate solution is to stick to trees that are native to your region – even better; native to one zone colder. In your situation, look to what grows in zone 4. There will be many who claim to raise out of zone trees without any issues. They either have a better setup than most, or they haven’t been doing it long enough. USDA zones are based on averages. As I’m sure you know, you may have several mild to average consecutive Winters, but then you will hit one with temperatures that are much more severe. A change of address is always a possibility too. I hoping for that myself. Although I’m halfway around the world from you, I sympathize because I also live in 5a. Unless you can swing a controlled temperature greenhouse, save yourself a lot of future grief and focus on zone 4 trees, or go with a tropical setup indoors. I wish you luck with whatever you choose to do.
