Prune your azaleas back within three weeks after blooming in the spring. If cut too late, you will be removing the buds for next season. Don't cut more than one third of the stem back at a time. If the azalea is leggy cut the branches back to different lengths and the new foliage and buds will fill in the plant within a few weeks. Use the three D's when pruning. Cut out Disease, Dead or Damaged branches. Also, if you have any crossing each other in the center of the bush, chose one to cut out to make the bush look better.