be nice and go underground and kill his heart, make him grow more with the stuff mother
maple gives you, make him stop growing with the stuff Father Poplar gives you, or be evil
and torch him with a flame or shishkebab

take a plasma rifle and shoot him he will scream

In oasis you will encouter a talking tree(herbert no wait bob) he will ask you to kill his
heart. Then you will encouter mother maple and tree father birch arguing they each give
you an item (father birch gives you an item to stop the growth of the tree and mother
maple gives you somthing to speed up the growth) just go in the caves and choose what you
want to do when you get to the heart (killing bobs heart gets you no karma change and you
get a perk called "barkskin" it raises damage resistance by 5%)