>>2671060I'm in zone 5a and it gets to -25 for a night or two every couple years. I have plum, apricot, peach, and pear cultivars meant for zone 5-9. They still produce, because an occasional few cold days won't harm a tree, and because they were bred to thrive in "zone 5", not "minimum temperature -20", which are different things. The map isn't calculated how you think it should be, or you don't understand what an average is, fine. But that's your error, not the USDA's. It's an objective calculation, and if you're growing something meant for zone 9 at the coldest, it should survive the occasional night in the low teens, because that's a feature of every location in that zone.
