One of the most important things to remember with flowering shrubs is that because of their different blooming dates, pruning at the correct time is critical. Shrubs may be thinned heavily by cutting some of the old branches back to the crown near ground level.
Diseased wood is pruned out to keep the plant healthy.
Diseased branches are cut back to non-diseased wood so that a healthy sprout will grow. This type of pruning should be done when the disease is first noticed, especially in the cast of fire blight of pyracantha, cotoneaster and quince.