Trimming an azalea bush gives the plant a better shape and makes it fuller by stimulating new growth. The two types of pruning are moderate and heavy. Deadheading is another procedure that keeps the plant healthy.
The best time to prune is early spring, before the annual new growth begins. Pruning stimulates the plant and encourages new growth. The next-best time to prune is while the azaleas are in bloom, or just after. Pruning after the middle of summer may inhibit next year's blossoms. Azalea buds begin forming as soon as the current crop of flowers fades away.
Moderate pruning involves cutting back of twigs every year or two, and is done when the plant is in good shape and not overgrown. This method simply cuts the growth of the previous year down to the first ring of leaves.
Heavy pruning is done to shape an azalea that has become unmanageable or spindly. This method is more severe and should be performed in stages to protect the plant. Heavy pruning involves cutting three to five of the largest branches back by one-third to one-half. Neighboring branches are then shaped. Heavy pruning is done in early spring to give the plant as much recovery time during the growing season as possible.
Deadheading is a form of light pruning. Sometimes a number of buds form on a single branch. If allowed to mature, these flowering buds crowd themselves out. By selecting a few buds and removing them, the remaining flowers grow to be healthier. Deadheading is also used to remove withered flowers.