Wait until the final frost in your area to prune frost-damaged plants. Ensure that the cold weather has passed for the season because early pruning can prevent the new season's growth from occurring, as pruning stimulates new growth.
During excessively cold temperatures
Plants are more brittle in cold temperatures. Messing around with them may cause branches to snap and split unintentionally. 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.
Summer flowering shrubs should be pruned in late winter or early spring. This still gives them time to set flowers for the following year. Deciduous shrubs that aren't grown for flowers can be trimmed back at the same time.
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.
DON'T prune during fall.
This can weaken and damage the plant—especially if there's an early frost.
Pruning at this time of year will severely weaken the plants. This is disastrous for the plants and all the hard work you did during the year to make your landscape beautiful.
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.
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 evergreen bushes is best done in late March or early April before new growth begins. Light pruning can also happen in late June or early July. Avoid pruning evergreen shrubs in the fall, since they are more susceptible to winter injury.
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.
While it is a good idea to hold back on water during autumn to allow plants to harden-off for winter, it is essential for shrubs to enter winter with adequate soil moisture. After a few light frosts in fall, irrigate shrubs deeply and apply a layer of mulch to regulate soil moisture and temperature.
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.
Shrubs in Ground
If you live in a harsh winter climate, you should do the following: Add 2–3" of mulch, leaves, or pine/fir boughs around the base of the plant. A heavy snow cover will also help insulate and protect the plant through the winter.
Cover Plants – Protect plants from all but the hardest freeze (28°F for five hours) by covering them with sheets, towels, blankets, cardboard or a tarp. You can also invert baskets, coolers or any container with a solid bottom over plants. Cover plants before dark to trap warmer air.
The easiest way to protect from a freeze is simply by covering plants with a sheet or a blanket. This acts like insulation, keeping warm air from the ground around the plant.
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.
Evergreens, in most situations, should be pruned in the growing season, since they never become fully dormant and may suffer tip burn if pruned in the winter. There are important reasons to prune at this time. It is much easier to prune a plant without its leaves since you can easily see its branching structure.
Mild fall weather may have you thinking about pruning shrubs and trees. But it's better to wait till late winter, or, at least, after leaves have fallen. Fall isn't the right time to prune trees and shrubs. There are good reasons to wait till late winter or after the plants' leaves have fallen.
Future frost events will kill the tender new growth and possibly the entire plant. You may not want to, but you should leave those ugly dead leaves in place through the winter. Wait to prune until the threat of frost in your area has passed and evidence of life within the plants is visible.
Perennials NOT to Cut Back
Also, do not cut back hardy perennials like garden mums (Chrysanthemum spp.), anise hyssop (Agastache foeniculum), red-hot poker (Kniphofia uvaria), and Montauk daisy (Nipponanthemum nipponicum). Leave the foliage. It's important to protect the root crowns over winter.
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.
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. There is less impact on the surrounding landscape and our crew can easily see what they're doing while all the leaves are gone.
If your plant suddenly wilts, leaves turn brown overnight, or the plant turns crispy or even black, this plant is most likely frost-damaged and finished for the season. Wait until the final frost in your area to prune frost-damaged plants.