Can you split a butterfly bush? How to prune a butterfly bush? How do you cut back a butterfly bush? In fact, butterfly bush pruning can take place just about any time of the year. However, certain pruning techniques will help promote more vigorous growth and healthier blooms.
Generally, most butterfly bush pruning should take place during the winter months, in warmer climates, while the plant is dormant.
Buddleia plants should be pruned twice a year: the first pruning is a hard-cutting in the spring, with a second pruning in the fall to cut away the spent flowers after the blooms fade away. Because the butterfly bush is a hardy perennial it will come back the following spring and offer plenty of blooms and beauty. Dispose of the dead flower heads and pruned branches.
The key to a healthy, blooming butterfly bush is to prune it back in later winter or early spring and provide full sun or as close to that as you can get. The less sun you have, the less blooms too. For your hydrangeas, if you are pruning , make sure you are pruning at the right time.
In such a case, one should always maintain a specific height of the bushes (at least feet).

