Of course, shrubs grow perfectly well without any pruning. But the shrubs in your yard will grow more vigorously and look better if you prune them routinely. Pruning is done for many reasons:
To control the plant’s size
To improve its shape
To remove weak, damaged, or dead branches and twigs
To encourage flowering by removing old flower clusters and developing seed pods.
To reduce insect and disease problems by opening up inner branches and leaves to better air circulation and light
To prevent damage from ice and snow
To renovate an old shrub by pruning out older wood. The new wood that follows will produce better flowers and form.
Before you start to prune a shrub, step back a bit and get an idea of how you want it to look. Begin by cutting out any obviously dead or damaged branches. Then prune to improve the plant’s shape. Check your work now and then from a distance. Pruning is not hard to do, and it’s fun to see how you can direct a valued plant’s growth to increase its value further and enhance the appearance of your property.
Maintenance vs. Renovation
There is a big difference between pruning a shrub to renovate it and pruning it every year or two as part of general maintenance and care. Renovation pruning requires removal of most or even all of the aboveground growth. This removes all the overaged woody stems to stimulate new growth. For example, you can do this with lilacs, boxwood, blackberries and raspberries.
If the shrub is in good condition, prune only as needed for maintenance. On smaller trees and shrubs, some routine pruning is useful almost every year. The secret to keeping the pruning job simple is to prune frequently, a little bit at a time, rather than waiting until the shrub gets too big for its space or develops an awkward growth habit.