the tree in my mother in laws yard is what she calls a 'tree of heaven'. i do not know the proper name. it is approximately 54 years old. i have noticed the inner part of the branches has a soft core. the core of a large branch that broke off in a wind storm this week is almost black inside. is this a sign that the entire tree is rotting inside and needs to come down or does certain parts of the tree just need trimmed back?