The practice of cutting all of a shrubs stems back to about 2 inches above the ground is called rejuvenation pruning. Cutting back a shrub to the base can be scary but new growth will appear and rapidly form near the cut. The benefit of cutting back to the base is that the shrub will maintain its natural shape. If you prune higher the new growth will appear where the cut was made and the plant will not appear in its natural shape. Cutting the shrub at a higher level will create a bush that is thin at the bottom and thick at the top.

If you prefer a less drastic pruning method, just annually prune 1/3 of the mature stems to the ground level (about 2 inches above the ground). In 3 years you will have a totally rejuvenated shrub that is made up of vigorous young branches. A good example for this type of pruning would be a mature lilac bush. Lilacs will respond to both methods of pruning but the 1/3 per year method may give you a little more peach of mind.