I was given this tree and I would like to start pruning it. Im confused as to what a sucker is and if this big secondary "trunk" is a sucker (the one that is lighter green and smaller). It is taller than all the other stems and branches coming off the other (darker, larger) trunk. All the branches that are from this "smaller trunk" are producing leaves but no buds. What do I do with this, if anything? Also, how do I prune this tree. The tree was purchased 3 years ago. Thanks in advance!