It's a major annoyance when trees pop up overnight and wreck your car. Don't get me wrong, I love that the trees grow and you have to keep paths clear, but trees becoming deadly overnight is pretty silly. So here's my suggestion: add a tree growth phase between "harmless to drive over" and "totally wrecks your car" where the trees instead take damage and revert to the previous growth phase when you drive over them. This way frequently used paths will stay clear, but you will still need to clear a path if you stay away from an area for long periods of time.
