Pruning in winter won't harm the plant, but it will reduce flowering in spring. If a shrub is severely overgrown, you may need to prune it in winter anyway. It won't bloom that year (or not as much), but it will return to full form the following spring.
During excessively cold temperatures
It's minor, but it could impact the look of a plant or create a haven for insects and diseases later. Don't prune when the temperature falls below 25°F.
After “how?", the second most-asked question we get about pruning is “when?” (Or, "Can I prune this now?") The rule of thumb is to prune immediately after bloom for flowering shrubs, in late winter or early spring for non-blooming shrubs (particularly for heavy pruning), and not after mid-August for any shrubs.
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.
Any gardening expert will tell you, (contrary to what you may believe) that pruning encourages new growth just when the plant is trying to go dormant and new growth doesn't have enough time to harden before the first frost and freezing temperatures hit. Pruning at this time of year will severely weaken the plants.
You should trim your hedges at the same time of year you trim most of your trees — late winter to early spring. If your hedge has gotten out of hand, power hedge shears may be the best way to begin. Follow up by hand with freshly sharpened hedge trimming shears to clip away all the stray leaves or branches.
Deep water plants before ground freeze, and continue to water during winter months when temperatures remain above freezing but without precipitation, Erect physical windbreaks. Wrap problem plants with burlap or other material to protect from wind and subsequent moisture loss to evergreen shrubs and small trees.
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.
Hollies are also a regular in home landscapes. Most of the time, pruning hollies in winter when they are dormant is a good plan. Trimming these evergreens helps keep their shape and appearance looking neat, as well as encourages new growth.
Prune most broadleaf evergreens now: abelia, boxwood, cleyera, elaeagnus, nandina, privet, and holly. Wait until after flowering for spring bloomers. Viburnums (both evergreen and deciduous) can be cut back hard to reduce size, but you will sacrifice flowers for the season.
Late winter is a good time to prune most plants. Because plants and their pests are dormant this time of year, pruning cuts can be made without the risk of pests and pathogens entering the tree through the wound.
The period between the full and new moon (third and fourth quarters) is best for harvesting, slowing growth, etc.
You probably already know just how fast shrubs grow and start to look messy. If you wait too long, your shrubs will start to become an eyesore. Pruning less of the plant but more frequently is by far the best for the overall health of it. We recommend every other month, which comes out to be five times per year.
To protect plants from frost, you will need to cover them to keep the moisture from freezing. While an unexpected frost can leave many gardeners scrambling to find anything to cover their tender plants; it is important to use the right materials.
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.
As mentioned earlier, watering plants several hours before a freeze is the first defense against damage. During a temporary cold snap, cover entire shrubs with burlap, sheets or blankets for insulation. For the best protection, use a frame to prevent the covering from touching the plants.
Late spring is an excellent time to prune evergreen shrubs in the landscape. Pruning just after the emergence of the spring growth will provide a basis for helping to shape the plant while retaining the natural look.
Prune all evergreens, except pine, before new growth starts in the spring or during the semidormant period in mid-summer. When pruning, follow the general branching pattern to maintain the natural shape. Remove dead, diseased, or broken branches anytime.
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.
Winter Pruning Yields a Better Result
Pruning when all the leaves have dropped from the tree makes it easier to view the best places to prune to maintain structural integrity. It also makes it easier to spot vulnerable areas, such as damaged or diseased branches.
Winterizing evergreen trees and shrubs involves protecting them from drying winter winds. To do this, erect a burlap screen on the windy sides of plants (usually the west and north). Drive stakes into soil before it freezes, and come back when temperatures are steadily in the 20s to staple or zip-tie burlap to stakes.
DON'T prune during fall.
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.
Despite the fact your plants are dormant and brown, they should still be watered periodically. Plants that remain dehydrated in winter months often don't survive until spring. Not only does this create extra landscaping costs in warmer months, it can actually damage your plumbing.
Late spring, early fall, or winter (when the hedges are fully dormant) are the best times for pruning hedges. Don't prune hedges during very hot, dry weather, and prune well before your first frost date.