Pruning can make plants hardier and help them over the winter too. Other plants, however, can't handle fall pruning—such as azalea, viburnum, Loropetalum, and lilac. If you prune a spring-blooming tree or shrub after its flower buds have formed, you'll be lopping away any opportunity for a spring showing.
Never shear a shrub in fall (or ever, actually, but that's another article) and leave major pruning or renovation for late winter/early spring, or immediately after bloom for spring-flowering shrubs.
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.
Don't Prune in Late Summer and Fall
Pruning shrubs in August or early September may encourage a late flush of growth. This new growth may not harden sufficiently before the arrival of cold weather and be susceptible to winter injury.
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.
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.
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.
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.
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. Pruning too soon can harm your trees and shrubs.So, when it comes to fall pruning, procrastination is the way to go.
You can trim boxwoods at any time of year, but you should avoid heavy shearing or pruning during the late fall and winter months, even if you live in an area where snow isn't a factor.
The period between the full and new moon (third and fourth quarters) is best for harvesting, slowing growth, etc.
A rough rule of thumb is to prune spring-blooming shrubs soon after they finish flowering because most bloom on old wood, while those that bloom in summer and fall usually bloom on new wood and can be pruned in late winter or very early spring.
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.
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.
Winter is usually the best time.
Without the leaves, you can easily see the branching structure of the shrub and decide what to cut. Dormant pruning is usually done in late winter, six to 10 weeks before the average last frost in your area.
Never prune too early in the winter, as incisions can dry out if the temperature drops well below freezing. When pruning, first prune out dead and diseased branches, especially those caused by the winter's snow and ice. Unwanted lower branches on all evergreen shrubs and trees should also be removed in late winter.
Follow The 1/3 Rule
It involves trimming around 1/3 of the branch, as cutting more than that may increase the chances of damage or stunt its growth. However, pruning too little will not give you the desired result.
Severe pruning means the cutting of branches and/or trunk of a Tree in a manner which substantially reduces the overall size of the Tree or destroys the existing symmetrical appearance, natural shape or health of the Tree and which results in the removal of main lateral branches leaving the trunk and branches of the ...
Maintenance or Standard Pruning is the removal of undesirable branches over 1 inch in diameter. Hazard Reduction Pruning is the removal of undesirable branches over 2 inch in diameter. This class is recommended where safety considerations are paramount.
The good news is that hostas, also known as plantain lilies, are tough and forgiving plants. Even if you forget to prune them at a certain time or you neglect to prune them at all, they'll still survive just fine, even if they don't look their best.
It's important to cut back foliage in the fall to protect flowering plants from disease and give them a clean start for regrowth as winter starts to turn into spring. However, there are some plants you can keep around through the winter since they benefit wildlife and still offer visual interest for your home.