You should not do aggressive pruning in summer. Major structural pruning should wait until the plant is dormant in winter. Improper pruning will stress the plant. You might cut off valuable buds.
Helps Control Disease
Some trees, like oaks, should only be pruned during the dormant season because they are especially susceptible to oak wilt disease, which is known to spread extremely fast in the spring and summer.
Pruning in August improves plant form just ahead of fall's growth spurt. Light shaping now will look beautiful after new fall growth arrives in the weeks ahead. Note: Plants should be well watered in the days ahead of pruning. Those that are experiencing drought stress should not be pruned.
Don't prune too late in northern regions.
In areas with cold winters, avoid pruning after the middle of August. If you prune too late, you may stimulate new growth that would not have time to grow thick, protective bark before the killing frosts of winter.
Few plants are pruned this time of year because pruning encourages new growth that does not have time to harden off before winter. Late-season pruning typically does more harm than good.
Summer is an excellent time for restorative pruning. You can correct problems that have resulted from over-pruning or poor pruning. You can also clean up damage from winter and spring storms. Proper pruning will begin to restore most plants' natural shape.
Summer pruning also keeps plants tidy and can allow you to provide better clearance, when necessary. Cutting back plants can also help you direct growth.
An improper cut like a flush cut (cutting too close to the trunk) or a stub cut (cutting too far from the trunk) can cause irreversible damage to a tree. A flush cut removes the branch collar and leaves a large wound in the side of the tree that won't heal properly.
Keep the height of tall summer-flowering perennials in scale with other plantings by removing up to one-third of stem height by mid- to late June. Cutting back these plants does delay flowering, so keep that in mind. It also causes plants to branch and become bushier, which means you'll have more flowers in the end.
Don't Prune in Late Summer and Fall
Pruning shrubs in August or early September may encourage a late flush of growth. This new growth may not harden sufficiently before the arrival of cold weather and be susceptible to winter injury.
The best season to prune trees is while they are dormant, or generally between November and March. This means waiting for them to lose their foliage and cease growth, but before forming buds. For fruit trees such as the apple tree, prune in late winter.
Summer pruning is best done in August-September, when the majority of branches have set a terminal bud.
Pruning in summer may encourage vigor. In summertime, weak tree growth should be pinched or pruned back about 3 inches from the end of each soft, leafy shoot. This can be repeated again in late summer if rapid side-shoot growth occurs.
Summer tree pruning plays a vital role in removing damaged, diseased, or dead branches. Any branch that can cause potential damage or stress to your tree should be eliminated. This promotes increased growth and reduces the chances of weak branches falling on your building during a storm.
Generally, the best time to prune or trim trees and shrubs is during the winter months. From November through March, most trees are dormant which makes it the ideal time for the following reasons: Trees are less susceptible to insects or disease.
April, May and June are not good months to prune because deciduous trees need to use their stored energy to produce new leaves instead of healing wounds. Also, pruning during warmer spring months encourages the spread of diseases such as Oak Wilt and damage by pests such as Emerald Ash Borer.
Tips on Summer Tree Trimming
Remove suckers, water-sprouts and branches that are crossed or rubbing each other. Take out “the three Ds” where you see them, too, (aka dead, diseased and damaged wood). Then the tree can direct its energy toward more vigorous branches and the production of flowers or fruit.
Plants that bloom on old wood (last year's growth) are pruned after flowering so as not to remove flower buds with a winter pruning. Hedges also require additional shaping in early summer, and fruits need a little training.
ALWAYS prune back to or just above a growing point (branch or bud) or to the soil line. NEVER leave a stem or branch stub. NEVER top a tree to “rejuvenate” growth.
Pruning during the growing season always stimulates new growth. During summer's heat, having to produce that ill-timed new flush of growth greatly stresses a tree. Pruning in the fall is even worse as it prevents the tree from going into a natural dormancy. The exception is heavily damaged, disease or dead wood.
Municipalities and homeowners often remove the lower limbs for pedestrian and vehicular clearance or to let the sun shine in for grass to grow. Mature trees, especially evergreens, benefit when healthy lower branches are left intact. Removing large limbs can increase the risk of decay.
Midsummer can be an excellent time for pruning flowering shrubs as long as you prune the right plants at the right time. In general, you cannot go wrong if you turn your attention to plants that have bloomed recently. Prune off everblooming roses after their first flush of bloom to encourage further flowers.
Well, it's a bit more complicated than that, depending upon the individual species. For the most part, pruning always stimulates growth, but how severely you prune a plant will depend on exactly what you want to happen.
Overgrown trees can pose a serious risk to your property and your family. Dead or damaged branches can fall and cause damage to your home or car or even injure someone. In addition, overgrown trees can block sunlight and views and can even damage foundations or driveways.