Renovating a Flowering Shrub
Old shrubs, such as spiraea, forsythia, lilac, and honeysuckle, often become overgrown and full of crowded stems and dead wood.
New growth is weak, and flower production decreases. To reduce the shrubs' size and width and rejuvenate them, follow these pruning techniques.
Tools and Materials
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, and 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 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 two to three years between severe prunings.
Improve shrub appearance and health. As the shrub regrows, 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.
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 by National Gardening Association