This requires cutting the whole plant down to a stump, and can be done on most broadleaf shrubs, such as hollies, azaleas, and camellias. Hollies, azaleas, and other non-grafted plants should be pruned to within 4 to 6 inches of the ground. Grafted plants, such as camellias, should be pruned to within 14 to 16 inches of the ground to avoid stimulating growth from the root stock below the graft. Junipers and boxwoods should never be pruned to stubs. Narrow-leaf plants, like junipers, do not have buds on their main trunks, which are needed to start new growth.
Boxwoods are very slow growers and so respond very slowly to severe renewal pruning.
Transplant boxwoods to a new location rather than pruning severely. The time for severe renewal pruning is just before new growth starts in the spring. To maintain a natural, informal effect on single trunk ornamental shrubs, first select the branch to be pruned and cut back to a lateral branch or a bud. When pruning back to a lateral, a good rule of thumb is to prune to a lateral branch which is one-third the diameter of the branch being removed. Following this guideline will help maintain the natural form of the plant.