Question: If I wanted to prune some of my shrubs back drastically, how much could I cut off, and when should I do it? Is it practical?
Answer: You can prune shrubs back rather heavily, but you do need to keep their genetic potential in mind. How tall would they be if you never pruned them at all? Try not to cut them lower than 50 percent of that height. Now, to your exact question, major pruning as you described should be done in late winter. That way you’ll be looking at stubble for the minimum time, plus the plants will be able to devote maximum energy to regrowing in early spring. You could probably remove as much as 30 to 40 percent of their top growth, but try to leave some foliage in place.