Okay everyone told me about leaving slack on the bottom to compensate for tree growth, I'm also familiar with setting the screws and fixtures a few inches away from the tree. But one of my jobs was just attacked by a wire-breaking tree, as it grew in circumference. To compensate, I'm now using a long slanted angle behind the tree instead of a nice and neat 90 degree angle which had concealed the cable. The issue is especially problematic where two wires split laterally to feed two fixtures, where the pull becomes doubled at the point where they split. I will no longer have them attached together like that, but use a long Y instead. If anyone has a method for how they hang and position some slack into the cable up by the fixtures, that looks nice and is effective, I would appreciate it.