Q: We have some lovely butterfly bushes that are getting too big for their space. When is the best month to prune them back?
A: Butterfly bush responds very well to yearly pruning in the winter. Blooms on this shrub are made at the tips of new growth. Severe pruning, which forces lots of new growth to emerge, results in more flowers to enjoy. How far down to make your pruning cuts depends on the mature size of your shrub. I used to prune my mother’s eight-foot-tall butterfly bush down to eighteen inches every January. You could reduce a four-foot-tall shrub to twelve inches without a problem.