question about zones
I am curious about zones. it is based on temperature/winter kill, right?
What is the actual mechanism of the tree dying?
I live in zone 5. lets say I have a tree that is zone 7, but the root stock is good in zone 5, then I graft a zone 5 limb onto the tree and a couple years later get a hard winder and kill the zone 7 portion. with the zone 5 part live, or even the cambium dead in the zone 7?
I'm not planning to try this, just trying to understand more about fruit trees.