I am still new to mini roses outside. When should I prune the gangly green canes they have become, and how far down should I cut them?
Well, I saw a lot of forsythia in bloom around Newark Airport this evening, so I would say that it is pruning time in our area. Take out all dead and damaged canes. How far down you cut depends on how tall they are. If you are comfortable, you can cut them down about half. If you are not, then just give a light trim. You can always come back and trim again after the first bloom cycle is over.