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.
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.
As a general rule, prune spring-blooming trees immediately after they flower. Prune trees that bloom in the summer or fall in late winter or early spring before the end of their dormancy. Routine pruning of dead or dying branches can be done at any time.
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.
In fact, it is better to prune a little at a time than to make drastic cuts. For plants that shed their leaves (deciduous plants), the best time for winter pruning is from the beginning of November to the end of February. To prune evergreens you can start later, from mid-December, and continue until February.
Spring flowering shrubs and trees.
Shrubs and trees like lilacs, azaleas, and others will grow best when they are pruned right after they flower in the spring. Avoid pruning them in the winter as it may stunt their growth.
Pruning in Winter Causes Less Stress for Trees
Research shows that pruning before buds open in spring leads to “optimum wound closure.” Trees are able to heal from pruning cuts before warmer weather brings out destructive insects and pathogens.
The best time to prune is after flowering. If the plant needs to be renovated, or severely reduced, this can be done late winter and early spring just before growth begins. Remove old flowers (deadhead) and cut back to healthy outward facing buds. Remove damaged, diseased, old wood and straggly growth.
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.
It is important to learn and understand the three T's of proper pruning: tools, timing, and technique.
According to gardening expert Mike McGrath, author of Mike McGrath's Book of Compost, and radio host of the show You Bet Your Garden, the rule of pruning is that you should NOT prune in fall. That's right, nothing and no exceptions.
Avoid pruning in fall.
Pruning cuts can stimulate new growth that, unfortunately, will be killed as temperatures drop to freezing. Trees and shrubs reduce their energy production as the growing season ends, so new growth in autumn will use a plant's stored energy reserves.
Don't Prune in Late Summer and Fall
Pruning shrubs in August or early September may encourage a late flush of growth.
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.
If you need to drastically reduce the size of a shrub or tree, it's often best to look at it as a long-term project, cutting off no more than a third at one time and giving it plenty of time to recover between pruning sessions.
Pruning Trees in Summer: Cut Conservatively
If you prune to excess in summer, next year, your trees may not be as full. Summer pruning takes away from the tree's total number of leaves, and fewer leaves mean less food flowing throughout the tree for next year's growth.
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.
Pruning Too Early
If you prune too early in the season, there's a good chance you'll snip the buds right off their branches, which means no flowers in the spring. Before you cut, do a little research, like with our pruning guide, or just wait to trim until the plant has finished blooming for the year.
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.
A much harder prune is done to regenerate a plant or to encourage lots of new growth from its base. Hard pruning is successful when plants can regrow from old growth or readily produce new growth from their base.
Choose the Right Time
Likewise, prune in the early morning or late afternoon to avoid the newly cut ends of branches becoming scorched by the hot sun. Wait 48 hours after rain to prune, to allow plants to dry out and avoid fungal diseases. When pruning, make cuts just above leaf nodes, or buds.
Did you know that if you prune too late in the season, you stimulate new growth, which will not have time to harden off before the first frost, which will be coming soon to our neck of the woods. This can weaken and damage the plant, so its best to leave the pruning until spring.
To avoid certain diseases, pruning in the late winter is especially great. Avoid Oak Wilt disease by pruning oaks between November and March.
Winter Pruning is Less Stressful for Your Trees
Pruning during the active growing season can cause stress for your trees and can stimulate additional growth that won't be able to harden before the temperature drops. Trees go dormant during the winter months, making it the perfect time to prune.
No matter what type of shrub you have, fall pruning can stimulate late-season growth that may not have enough time to harden. This can weaken and damage the plant—especially if there's an early frost. Instead, wait until winter and trim bushes when the plant is in deep dormancy.