Several of my forsythia bushes (which I started from cuttings about five years ago) have grown a large number of single, straight, six foot single stalks with no sign of branching although leaf buds are there. The bushes also have a few of the normal bending flowering branches that I expected. What should I do with these whippy stems? Prune them? or leave them and see what happens? Some have grown out of stems I pruned last year. Thanks for your help.