Start with clean, sharp, good-quality tools appropriate for the job at hand. To prevent the possible spread of disease, clean your tools after pruning each plant with a solution of one part chlorine bleach or rubbing alcohol diluted with ten parts water. A spray bottle of solution works efficiently and reduces mess.
Mature flowering shrubs benefit from a pruning every two to three years. This helps maintain the plant's health and vigor and enhances its appearance.
Step 1: First, remove any dead or diseased wood. Next, select two to four of the oldest, largest stems, equally spaced around the shrub. When removing old stems, try to make the cut as close to the base of the stem as possible.
Step 2: You may need to prune some of the younger stems and suckers as well—start by removing any branches that are crossing or rubbing against each other, then prune those that look out of place or are crowding the centre of the plant. Aim to leave a balanced variety of old and new, big and small stems.
Step 3: In general, to head back a stem that's too long, make the cut just above a bud that is facing in the direction you want the new growth to go—usually toward the outside of the plant. This keeps the centre of the shrub open, which is important for good air circulation, and looks more natural. If the plant has opposite leaves and one bud is facing in the wrong direction, simply rub it off. Do not leave stubs above the buds, as they will die.
How to rejuvenate an overgrown shrub
It may be necessary to take more drastic action to rejuvenate an overgrown flowering shrub: cut back all stems to within five centimetres of the base in late winter or early spring before new growth starts. Flowers will be sacrificed for the first year, and it may take a season or two for the plant to recover completely, but the overall improvement can be dramatic. Once the plant has returned to a normal size, implement a regular two- to three-year pruning regimen.