As long as there is good drainage where the butterfly bush is planted, you can prune it at anytime of year. In zone 8, you can prune bushes all the way to the ground or shape them.
About this Author
Susan Steele has been writing for more than 20 years. Her work has been featured in online publications, such as eHow.com and StarReviews. While attending Ashland Community and Technical College, Steele says her favorite courses were English and literature. Steele has enjoyed working for Demand Studios since June 2009.