Determine Flowering Time
The best time to prune depends on when the shrubs bloom. Prune spring bloomers in early summer, right after they finish flowering. Because summer-blooming shrubs produce flowers on shoots grown in the current year, wait until early next spring to prune.
Remove Dead, Damaged, or Diseased Wood
You can do this at any time of year. Prune into healthy wood or cut the shoots back to the ground. Also remove limbs that rub against one another.
Remove the Oldest Shoots
On shrubs with many crowded shoots, use loppers or hand pruners to cut about a third of the oldest shoots back to the ground at the right time of year for pruning a particular shrub. You can repeat this process each year, removing a fourth to a third of the shoots each time.
Prune Some Shrubs Severely
Some shrubs can tolerate having all of their shoots cut back at once to within 3 to 6 inches of the ground. To allow the shrub to recover in the following growing season, do this in late autumn to early spring. Suitable shrubs for this treatment include redtwig dogwood (Cornus stolonifera), smokebush (Cotinus coggygria), peegee hydrangea (H. paniculata 'Grandiflora'), ninebark (Physocarpus), basket willow (Salix purpurea), and spiraea bumalda. Allow 2 to 3 years between severe prunings.
Improve Shrub Appearance and Health
As the shrub re-grows, choose the strongest shoots and remove crowded, spindly, and weak ones. Prune off spent flowers, and cut the shoot tips back to a desirable branch or bud to encourage bushiness, but take care not to remove developing flower buds.
Take Precautions When You Prune
Safety glasses prevent sharp branches and sawdust from accidentally scratching or poking your eyes. Wear leather gloves to protect from pinches, splinters, and cuts.
With slow-growing shrubs and those with few shoots, prune lightly instead of renovating them. Remove the oldest and weakest growth at the appropriate time of year, but never take more than a fourth of the plant at one time.
Photography and article provided by National Gardening Association