Pruning Reminders for the Late Winter
Pruning Reminders for the Late Winter
One of the most common mistakes made with pruning is pruning unnecessarily. Another common mistake is pruning at the incorrect time of the year and injuring the plant that is being pruned. By pruning a plant that flowers on new growth at the inappropriate time, flower buds can be cut off and result in a lack of flowering. Issues with frost damage susceptibility, insects, disease, and sunscald are also potential results from improperly timed pruning or pruning that is done excessively or incorrectly for the plant that is being pruned. In order to avoid these potential pitfalls, it’s important to first ask yourself what is the goal of your pruning, as well as to know what species you are pruning and when it needs to be pruned accordingly. Some example reasons for pruning include: to train young trees, to maintain plant health, to improve ornamental aesthetics, to manage growth and size, to increase light under the tree canopy, and to improve safety.
Some plants, such as summer- flowering and fall-flowering shrubs that bloom after May (examples include Abelia, beautyberry, butterfly bush, rose of Sharon hibiscus, crape myrtle, and summersweet) flower on new growth. With these plants, any excessive pruning should be done in the late winter or early spring when the branches are still bare- this will reduce the likelihood of any pruning wounds taking a long time to heal/seal as well as a lower chance of insect and disease issues that are likely in the warmer months. This will allow new growth to flourish and result in beautiful blooms during the flowering season. Late winter is also when many fruit-bearing plants, such as blueberries and apple trees should be pruned.
Another winter pruning opportunity is to prune older deciduous trees in the late winter. While trees are dormant it is much easier to see their branches and the full shape of the tree. There are some things to look for – such as damaged/dead branches, diseased or insect-infected branches, and branches that are rubbing against each other. Removing any branches that fit the above characteristics is a great place to start pruning. From there, the tree can be assessed based on its species and if it has any greater need for pruning. By doing regular maintenance pruning, the need for excessive pruning is reduced. There are also some trees that are prone to bleeding out sap when they are cut (birch, honey locust, maple, dogwood, elm, and walnut) and while this does not hurt the tree, if these trees are pruned in late spring, summer or fall they will not bleed out sap.
For branches that are less than 1/2 – inch in diameter, hand pruners are the best tools and the preferred type for a clean-cut are the Bypass pruners. On larger diameter branches, tools such as loppers (branches up to 1 ¾ inch in diameter) or a hand saw (anything larger than ½ inch in diameter) are better suited. Making the pruning cut at the appropriate spot on the branch is important to preventing injuries. The branch collar is the part of the tree branch that is slightly swollen and just outside the connection between the branch and trunk of the tree. When pruning a tree branch that is connected to the tree trunk, the cut will need to be just outside of that branch collar area on the branch itself. This allows the tree to heal that wound itself and will not require any additional support and without injury to the main tree trunk, which means a cleaner cut and a healed wound without any disease or insect issues entering through the wounded cut area.
When cutting shrubs, the two most common cutting techniques used are heading back and thinning. Heading back is useful when the goal of pruning is to encourage growth below the cut, and if done too often without thinning cuts as well, it can result in a dense top canopy with reduced sunlight reaching the inside of the canopy, thus resulting in a loss of foliage. When making a heading cut, the terminal (end) portion of a woody branch is cut back without regard for the buds or lateral branches. Thinning cuts are used to open plants up rather than encouraging excessive amounts of new growth, and the branches are cut at the point of origin from their parent stem, so that would be at the branch collar, at the connection to a lateral side branch, or at the branch junction. The best practice with thinning is to remove the oldest and tallest stems first. If plants are repeatedly thinned without being headed back for multiple years they will likely have long and spindly branches.
There are a few spring-flowering shrubs that flower before May and bloom on old wood (flower buds are formed the previous summer or fall) that should not be pruned until right after they bloom (when flowers fade in the spring). These include forsythia, deutzia, lilac, viburnum, mock orange, and spirea. These plants should not be pruned in the late summer, fall, winter, or early spring if maximum flowering is desired.
Much of this information, including photos and diagramed pruning illustrations can be found online through the NC State University “North Carolina Extension Gardener Handbook”.