The best time to prune an azalea bush is in late spring or early summer just after the plant finishes blooming for the year. Pruning later in the summer, in the fall or in the winter removes the buds that are already developing for the following year.
Azaleas are early blooming bushes and are typically done blooming by early summer. The ideal time for pruning is within three weeks after the bush finishes blooming. The flowers begin to discolor and shrivel up as a sign that the bush is done blooming for the season. Waiting too long to prune the azalea bush may result in no or fewer flowers the following year because the buds get cut off.