I planted 1 prune plume tree 3years ago and one 1 year ago.the 3 year old is growing into fhe sky ,lots of branches and the 1 year old one is not far behind,not as many branches.how do I prune them?I hear they need the center open?the 3 year one is a dwarf mount royal and the other a stanley semi-dwf dlx.do I cut the tops down so far ,the center out?please some one help.I have not seen a plume yet.also when do I do the pruning?the 3 year one also has some kind of agrowth on one of the branches,looks dark and bumpy.so please help

sigrid-hilde