My wife has a few mulberry trees. They are less than 6' tall but one of them is turning into a bush. It has 3 main stems and 3 new suckers this year. She wants a tree not a bush so I figured I'd just hack off hte suckers and leave 1 or maybe 2 of the main stems. She recalls hearing that you should not prune mulberry trees because they bleed too much. assuming it's true would they bleed or be adversly affected if I pruned them in the fall or winter?

Thanks