Although over pruned trees and shrubs don't usually die if some part of the canopy remains, the damage from over pruning can be extensive. Over pruning reduces the foliage that's available for making food for the rest of the plant and can allow pests and diseases access to the tree if cuts are made incorrectly.
Over pruning reduces the foliage needed to make food for the tree, so in effect, it starves it. When a tree has been over pruned, you may not see much new growth during the spring. In the winter, more branches than usual will break as a result of heavy loads.
How to Fix an Over-Pruned Tree or Shrub. While some plants need a heftier prune than others, in general, the golden rule is to trim no more than 15 to 20 percent of a tree's canopy at one time. Keep that in mind for next time.
Over-pruning any time of year. It is especially important to avoid over-pruning during the growing season, but over-pruning any time year can stress a tree, making it more susceptible to disease. It's important to remember that every pruning cut matters because every cut is a wound to the tree.
Don't cut off leaf and flower buds.
For example, rhododendrons and conifers are best pruned in late summer before they set buds for the next year. You'll face a similar lack of blossoms if you prune spring-flowering trees and shrubs in late winter or early spring.
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.
The basics of hard pruning
The hard pruning approach involves cutting the entire plant down to around 3 to 6 inches from the ground in very early spring before any foliage is emerging. This timing will minimize stress on the plant and direct energy into the growth of new stems.
One general rule of thumb is to wait until your tree has grown back to its original height. This should take some time, giving your tree some rest and time to heal. After this, it's possible to start pruning your tree again, enabling you to shape your tree how you like.
After Pruning Your Houseplants
If your plant is nice and healthy, it should recover from pruning and begin growing again within a few weeks. If your plant gets a little droopy for a few days, don't worry. It might be experiencing shock, but it will bounce back.
The 1/3 rule involves cutting about 1/3 of wood during any pruning activity. This moderate pruning practice is a balanced approach to thinning out shrubs to stimulate new growth. The plant loses a good amount of stems, usually on the top section, allowing more light and air to enter the inside of the plant.
Watering is very important during the couple of weeks or more that a plant is recovering from root pruning. Right after pruning, I give the whole pot a thorough soaking. As new growth begins, I make sure to thoroughly wet all the soil at each watering.
Pruning at the wrong time can send a plant into shock, stunt its growth, or cause it not to bloom that season. It can take years for a plant to recover, if it can. Heavy pruning is best done when a plant is dormant.
As a general rule, a light summer pruning can be performed on most deciduous trees and shrubs. Heavier pruning should be performed when the tree is dormant, preferably in late winter before active growth begins.
Generally, plants are cut back by about one-third of their height. After pruning, apply a fertilizer to stimulate vigorous new growth. Many perennials that have finished blooming may be cut back now as well.
According to Ramsey County Master Gardener Volunteers, February is the best time to prune your trees. In February, harmful tree diseases are at a minimum and deciduous trees have already “hardened off”, meaning they have prepared for winter dormancy.
After a tree is topped, it grows back rapidly in an attempt to replace its missing leaves. Leaves are needed to manufacture food for the tree. Without new leaves, the tree will die. The new branches that sprout up below the cuts will continue to grow quickly until they reach the same size it was before it was topped.
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.
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.
As a tree grows, branches do not move farther off the ground. Prune off the low temporary branches gradually, over a course of several years, and before they reach one inch in diameter. Never remove more than one-fourth of a tree's branches at one time.
For most trees, the best time for major pruning is late winter to early spring because wounds close faster. Pruning in late summer and early fall may also stimulate new growth, which has little time to harden before cold weather comes.
In pruning, there are three primary types of pruning cuts, thinning cuts, reduction cuts, and heading cuts, each giving different results in growth and appearance.
The node is where leaves, buds and shoots emerge from the stem. You should always cut just above a node, as this prevents 'die back' and therefore disease. Also, by cutting above a node you can manipulate new stems, leaves or flowers to form in a desired direction, as nodes form on different sides of a stem.
The answer is, it depends. There are certain trees that should always be trimmed in the summer, certain trees that should never be pruned in the summer, and unavoidable situations in which a tree needs to be trimmed no matter what time of year it is.