Trees are woody weeds once you don't want them or when they die. I only remove nuisance trees and some dead trees. Two red oaks 100' from the house died, they got to go. A large volunteer cherry and a previous owner planted pear tree were blocking too much sun from my garden beds. They have since been removed. I transplanted a volunteer mulberry into the open field. I also have trees which I dug up from my truck driving days and a vacation. Maine, Minnesota, NH, and Pennsylvania are some of the states.
Copper does work. At my previous residence I shot at targets resting up against a loblolly pine tree, it did die, I cannot remember how long it took.