In February, harmful tree diseases are at a minimum and deciduous trees have already “hardened off”, meaning they have prepared for winter dormancy. When the growing season begins, the wounds will be sealed, and the healing process will begin. July and August are the second-best times to prune.
Most trees should be pruned during the late dormant season (February through March). February through March is generally regarded as the best time to prune most deciduous trees.
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.
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.
There is never a bad time to remove dead, damaged or diseased branches. But most trees benefit from pruning in mid to late winter. Pruning during dormancy encourages new growth as soon as the weather begins to warm. The lack of leaves after autumn allows you to easily identify branches and limbs requiring removal.
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.
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.
Surely there's one chore you can tick off your endless outdoor to-do list—and maybe even get a jump on for spring. The rule on fall pruning is, generally speaking, don't prune in fall. But there are a few trimming tasks you can take on with confidence, provided you approach the job with self-control and a plan.
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.
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.
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.
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.
Fall is the time to clean up any dead, damaged, dangerous, or diseased branches but otherwise, hold off. Most pruning tasks are best done in the winter or early spring when plants are still dormant and not budding or blooming. That's the time to prune for better appearance, structure, air flow, and so on.
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.
Branches that Double-cross or Grow Inward or Grow Downward:
Similarly, branches that grow inward toward the central stem or trunk are likely to end up chafing against other parts of the plant, so it's best to prune them.
Don't shear the branches of spring flowering shrubs (Forsythia, Lilac, New Mexico Privet, Spirea, Flowering Quince, and others). These shrubs produce flowers on last year's wood, so removing old growth will reduce or prevent flowering. These plants should be pruned immediately after they are done blooming.
By not cutting back the statuesque achilleas, eryngiums, perennial astilbes, sedums, alliums and many ornamental grasses, you can enjoy their structure against a winter sky. The sight of their stems silvered with frost adds a whole new level of interest to the garden.
For a tree to completely compartmentalize and seal off the exterior of a severed branch, it may take upwards of 15 to 20 years. However, within the tree, this containment process is fast-paced and extremely effective.
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.
Young trees should be inspected and trimmed every 1-5 years. Mature trees may benefit from a yearly inspection with perhaps a five- to 10-year cycle of trimming and pruning. Fruit trees may need to be trimmed annually. Hire a qualified arborist to trim 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.
Differences Between Pruning and Trimming
Webb said pruning typically involves removing dead or diseased wood and thinning out stems and branches to improve the overall health and appearance of a plant. On the other hand, trimming typically involves cutting back plant material for reasons other than health concerns.