Pruning is necessary to obtain a full, well-branched azalea. The best time to prune is shortly after flowering, but not later than early July. Since flower buds are formed on the previous year’s growth, pruning too late in the season will reduce the number of flowers the following year. Also, fertilizing 4 times a year with an acid-forming blend such as 12-4-8 or 15-5-15 will promote good growth and health.

Additional Resource
http://edis.ifas.ufl.edu/MG019