I don’t see any reason you can’t prune a tree and take off a staff or a wand, and in many cases pruning a tree can hep it. Just be sure you don’t cut into the bud or damage the bark, a big branch will require several cuts, starting at the bottom and then from the top. Cut as close to tree as can, but do not cut the bud where the branch comes out of the tree. I would tell the tree what you are about to do and explain why. and then there is that idea of running water, and you have to take it out of the stream in the direction the water is flowing to get the energy. lot’s of witches are really into the energy, and they must have a reason for it. whatever you do, don’t damage tree bark, or carve initials into tree because that is bad juju. I have had trees tell me they don’t like metal objects around, or at least the tree spirit told me that. and the trees seem to know when a druid or witch is around it, but I really at this point don’t see a lot of difference in a witch and a druid, they are both Neo-pagans. I think the druids liked the oaks because there seem to be a lot of awen around oaks, and oak tree spirits can be easy to communicate with, and if a tree does become your friend, you will find yourself hanging out around the tree. I also find it interesting how all the young children in a neighborhood will gather under an old oak tree. They really can be very friendly. but I guess trees can have personalities like people do, and some trees probably just don’t like humans at all. I would think if a tree was really mad about you taking a part of it for a wand or a walking stick or a stang, the tree would tell you. I know it would tell me. So I would probably ask if its okay before cutting, and if I did not hear anything back, I would tell the tree what and why I am cutting the limb, explain to it that it was in no harm, but there are some cuts that require that you seal the cut with something afterwards, so that would probably be important to know what trees need what.