Do I need to cut back our butterfly bushes, and if so, in the early spring or late fall, or winter?
The Gardener’s Answer
As gardeners, we prune to thin, shape, and rejuvenate our flowering shrubs. The correct time to prune them depends on what the shrub is and what time the year it blooms. As a general rule, we prune spring-flowering shrubs after they have finished blooming. This includes all plants that flower before June 1.
For the summer-flowering shrubs, those that bloom after June 1, they should be pruned during the winter months or in the early spring before new growth begins. Butterfly Bush (Buddleia) are considered summer-flowering shrubs so, the best time to prune them is late winter/early spring before new growth begins. Pruning now may encourage new growth that can be damaged by any early frosts. Pruning while they are dormant will make them less susceptible to winter injury and other potential problems.
If your reason for pruning is to remove dead/diseased or crossing branches, go ahead and get your pruners out. Otherwise, waiting until later in the winter or early spring before they break dormancy would be in the best interest of your butterfly bush.
It is best not to remove more than one-third of the size of the shrub at one time. Do this year after year to maintain the size you want. Use a clean, sharp, and rust-free pair of pruners. Make your cuts flush to the nearest intersecting branch so there are no stubs. If you need proper pruning instructions, learn more here.