You can save the cost and effort of replacing a valued, otherwise healthy overgrown shrub by using good pruning techniques to revitalize it. Renovation involves cutting the oldest and thickest of the stems down to ground level and removing them. The basic rule of thumb is to cut out no more than one-third at a time. This way, the shrub continues to have a presence in the yard. Meanwhile, the pruning stimulates its root system to send up supple, vigorous replacement stems. If done gradually over a period of six years, this process completely renews an old shrub.