I planted 2 River Birches a couple years ago along our walk. They never did very well and I would like to remove them. They were both balled-and-burlaped and each have three trunks about 3-4" diameter each. They are somewhat tall (about 20 feet or so and rather whispy). My question is this. Can I just use a Sawzall and cut the trunks flush with the ground and leave the root ball in the ground or will the root ball cause decay issues? Also, what would be the best tool to use to remove some of the roots so that I might be able to plant something small where the trees were?