I relative of mine, far away and long ago (the statute of limitations has run out and he has died) once had land on which he got paid to rent a billboard (advertising cheap gas along I-75). Trees grew up in front of the billboard, and the ad agency did not want to rent the space anymore, as the billboards were covered from view by the trees, which were between the sign and the highway.
So he had a guy drive a copper nail into the tree, which, of course died. I am not sure of the number of copper nails that were needed, but copper is toxic to many plants.