How to Prune Shrubs
Too many people are afraid of pruning shrubs. They’re willing to put up with scraggly appearances in foundation plantings and hedges, rather than chance hurting the plant. Actually pruning does positive things and aids plant growth. Instead of thinking that you are only taking away growth from a plant by cutting, look at it this way: You’re preserving the natural character of the plant, encouraging larger and more abundant flowers and fruits; you’re restoring old plants to health by removing injured or diseased branches; and finally, you’re giving the plant a better balanced, more attractive shape.
In fact, many experts believe that at some time or other every branch of a shrub should be taken out in order to make room for younger growth. Almost every shrub which blooms in spring bears flowers on wood that develops right after blooming time. These branches grow rapidly during late summer and fall, producing many blossom buds. If these plants were pruned in late fall or winter, instead of summer, most of the flower buds would be cut off. Summer is also preferred since the desired shape can be better achieved when the shrub has its full leaves.
Different Pruning Times for Different Shrubs
The following shrubs are pruned immediately after blooming: deutzia, dogwood (except berried varieties), fringe tree, forsythia, golden currant, bush honeysuckle (except fruited varieties), lilac, magnolia, mountain laurel, pearl bush, mock orange, azalea, flowering quince (unless fruit is desired), rhododendron, climbing roses (except those producing edible rose hips), snowball, spring-flowering spirea and wigela.
Shrubs that bloom in summer and fall, along with spring-blooming varieties bearing desirable fruits, are pruned just before growth starts in spring. Some of these are barberry, hibiscus, abelia, coralberry, hydrangea, snowberry, fruited viburnum, summer-blooming spirea and fruited-bush honeysuckle.
With early spring-blooming shrubs like forsythia and spirea, keep the plant in good shape and flowering by taking out entire branches near the ground level. If there is an abundance of new stems rising from the ground, take out the old dark and dull-colored canes right at the soil surface.
If there are no extra stems, cut back all the braches to two or three healthy buds, or to three or more low side branches near the bottom, so the plant won’t be killed by weather extremes. When branches become extra long (as so often happens with forsythia), Howell advises heading them back during the summer once they reach their desired height. The shrubs will then put out side growth instead of added height.
For shrubs like firethorn and Japanese quince, cut back about one-third of the plant and remove thin wood annually in early spring. Also cut back any scraggly, awkward-looking branches to another side branch lower down the stem.
Unless lilacs are pruned regularly, they have a tendency to become too tall and leggy. The young suckers and dead wood should be removed along with some older branches, so that more light reaches the center of the plant. Just as with other shrubs, lilacs should be cut almost to the ground if they have been neglected for too long. Remember to give each branch enough room to grow.
For azaleas, rhododendrons and magnolias, the stems which carry blooms should be pruned as soon as the flowers begin to fade. The cuts should be made on the flowering branches just above the first pair of axil buds. Young plants may be cut occasionally to foster vigorous growth; here again overgrown, neglected plants can be cut back drastically in early spring.
Shearing is not recommended for upright evergreens that have become too large for the location. If this happens, cut off the longer branches just above smaller side ones. Another frequent problem is the damaging by storm of an evergreen’s central growing tip. Gradually, one of the stronger side braches will grow faster, straightening up little by little. To encourage this transition, fasten a stake to the trunk and gently bend the side branch upward and tie it there. Soon it will take is proper place as the upright leader.
When shrubs have been neglected and are full of suckers, are ill-shapen, and a tangle of weak growth, it may be necessary to cut the entire plant right down to the ground. Leave just a few inches of growth. This drastic action should be taken in early spring; the result will be a new top for the shrub. As the young shoots grow, they can be pruned or thinned to make a shapely shrub. This method is advised for deciduous plants such as forsythias, snowberries and others that are vigorous growers.
Many nursery and garden center experts advise cutting back hedge plants to half their height at planting time. After about one foot of new growth is made, they suggest cutting back another 50 per cent to encourage vigorous branching. By the third season, plants are on their way to a permanent shape.
It doesn’t take a great deal of talent to give proper care to your flowering shrubs. Point number one is not to be afraid. You’re not fighting nature, so don’t have a guilt complex about pruning.
Generally, flowering shrubs are most beautiful if allowed to follow their natural, informal shape. Your objectives are to cut out injured branches—in some cases—back to the ground; other times all you may want to do is shorten canes to a reasonable length.
Sometimes you may make a mistake; but most times, you’ll improve the over-all appearance and growth of your plants.
The University of Illinois Extension offers these two excellent pages about Pruning Shrubs.
See our page of cutting heights for different varieties of grasses.