i wonder about the tree adapting to the environment. giovanni's Paradiso in PA doesn't get frost damage any more i heard. first few yrs, it died down to ground, but now it's unprotected in PA winter without damage. i know older trees will take cold better. does that mean there is some genetic mutation that helps tree to survive in cold weather better? or the tree's mass and growth has reached certain point where the freezing weather just won't damage it much... if it's genetic mutation, then it will be a different tree and cutting from the tree's new growth will be better suited to colder weather. but if it's just bigger tree handling cold weather better, new cutting will have to go through the same die back year after year.