Azaleas, i.e., flowering shrubs that grow well in shady areas, require pruning for optimal flowering. You will need to determine when to cut the shrubs, which branches to get rid of, and avoid over shaping the azaleas. If your azalea is infected, extra precautionary measures should be taken to avoid spreading the disease.
In general, it is best to prune azaleas before they flower, typically in the first part of spring. This gives the shrubs ample time to fill out and allows any new growth to become mature enough to withstand the winter. While pruning azaleas at this stage can limit the amount of flowers on young shrubs, it is typically the best way to ensure an abundance of flowers in the future.
Pruning removes old or dead branches, thereby allowing new growth to sprout. If you prune azaleas any time after the middle of summer, you can significantly reduce the amount of flowers produced the following spring. It can also put the shrubs at risk of damage during winter because new growth prompted by pruning typically does not have enough time to mature.
It is typically best to begin to prune azaleas by removing any dead branches from the shrubs. You will be able to tell if a branch needs to be removed by gently nicking it with your gardening shears. If the wood underneath the surface is not bright green, it is generally best to remove it. To do this, cut the branch to either the healthy branch it is coming off or one foot (.3 meters) off the ground. You may also want to remove two to three of the oldest branches from the shrub in the same manner to promote growth. Pruning any more than this can shock the plant; the removal of old branches is best done over a period of years rather than all at once.
Once you've removed the bad wood, look down into the center of the shrub. If it is overgrown, the azalea will be unable to get enough sunlight or water at the bottom, thereby limiting growth. Working one branch or stalk at a time, prune azaleas with sharp shears until the center of the plant is thinned out. It is typically best to examine an azalea after each cut to ensue you do not over prune it.
While many shrubs do well with close shaping, azaleas grow best when left in their natural state. You can prune azaleas to prevent them from appearing shaggy or overgrown, but this type of pruning should be limited. Attempting to cut the shrub into an unnatural shape can significantly limit growth and reduce the amount of flowers it produces.
Pruning azaleas that are infected with a disease requires you to take extra care. Once you've determined which branches are infected, cut the first one and remove it carefully from the shrub with gloved hands. Before cutting another branch, clean your shears with a sterilizing solution. Continue this process until all of the infected branches are removed.