I have a box hedge that was originally trained into balls, but sadly has been left without pruning for about two years. Is it still possible to prune them back to the ball structure, and if so when should I attempt it?
I don't see why not. The usual time for pruning box is around Derby day in early June. It can be done from then into mid or late July. Any new growth that forms later than that won't have time to harden before the frosts and can be badly damaged.