While early spring is a great time to prune most shrubs, it is best to prune early-Spring bloomers right after they bloom, preferably within six weeks. As our azalea, rhododendron, viburnum finish blooming, it is important to perform the most aggressive pruning on these shrubs in May and June. Spring-blooming flowers bloom on the wood formed the previous year, so it is best not to prune them until after they have bloomed. Soon after they finish blooming for the current year, they begin to set the blossoms up for the next year. This allows the new branches to be prepared to bear the new blooms by the time Spring rolls around the following year. If you prune any later, you will be cutting off the next season’s flower blooms, which means that your shrub will not be reaching its’ blooming potential.

Virginia Residents can also reference Virginia Tech’s shrub pruning calendar for specific pruning intervals for your ornamental shrubs!

 

Link: https://www.pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/430/430-462/430-462_pdf.pdf