This is more of a general hardiness question actually. Most species have a large hardiness range. Does this range just indicate where the species is found, or the extremes any individual of the species can tolerate?
I'm asking mainly because of an American hornbeam I purchased though. They are species that is hardy in zones 3-9. I live in zone 5. This tree was collected in zone 8. Since it was growing in zone 8, is it best to assume it's not going to be hardy in zone 5 even though it's a species where at least some individuals can live in zone 3?
I'm torn as to whether I should treat it as a zone 8 tree (let it freeze lightly a few times, then move it to the greenhouse), or as a zone 5 - overwintered completely outdoors in a sheltered spot, like I do for my trident maples. Or can it just be treated as a full zone 3 and be set on the ground and ignored all winter.
I'm asking mainly because of an American hornbeam I purchased though. They are species that is hardy in zones 3-9. I live in zone 5. This tree was collected in zone 8. Since it was growing in zone 8, is it best to assume it's not going to be hardy in zone 5 even though it's a species where at least some individuals can live in zone 3?
I'm torn as to whether I should treat it as a zone 8 tree (let it freeze lightly a few times, then move it to the greenhouse), or as a zone 5 - overwintered completely outdoors in a sheltered spot, like I do for my trident maples. Or can it just be treated as a full zone 3 and be set on the ground and ignored all winter.