Decembers Newsletter: Winter Tree Pruning

As the title of this article says “Winter Tree Pruning;” but wait, I didn’t think tree could be pruned in the winter and that it’s bad for the tree. This is what most people believe or have been lead to believe by friends, family, and tree companies. The main reason for this concept is that majority of people and tree companies would rather work in heat than work in the fridge cold and windy winters. The truth is that winter best time to prune a tree, even though early spring, late summer to almost fall are also good times as well to prune a tree too. The rest of this article will cover the reasons that make winter the best time to prune trees.
Energy acquisition is not disrupted:
Trees complete a complex life cycle each year in order to survive and thrive; that has evolved from hundreds of thousands of years of growing. This is a simple overview of the trees life cycle. A tree from the beginning as a seed uses what energy it has to create roots to absorb energy to grow a trunk, branch(s) and leaf(s) for the single purpose of harvesting light for energy. The tree harvests the largest portion of its energy supply through its leaves. Light is absorbed by the leaves and then through photosynthesis process that light is turned into sugar; which is also known as sap. The tree stores the energy created by their leaves in its trunk and root system during the winter. Then comes summer and the stored energy created last summer is used to grow leaves to start producing more energy to grow, heal, fight off disease, and insects, and store once again for the winter.
Properly pruning during the winter is beneficial because the pruning isn’t disrupting the tree from its acquisition of energy. Winter pruning should be structural to get rid of rubbing, crossing, co-dominant, dead, and diseased or infected branches; but this should never exceed 25% removal of the trees canopy. This allows the tree to from buds in spring and creating leaves on fewer branches requiring less energy. Now, one could argue that removing the branches of the tree would grow less leaves in the spring would hurt the tree because it can’t produce enough leaves to in turn, produce enough energy for the next winter. There are two factors to take in consideration here one was stated earlier that only 25% of the canopy should be removed, and secondly the majority of trees grow too many leaves for their own good in the urban environment. Trees in the urban environment get to spread out and often have far less competition for light; so they produce more leaves to absorb more light. Another way to think about the tree canopy is as the ocean; the deeper you go the less light penetrates; same goes for trees, thicker the canopy the less light penetrates. This means that the leaves in the middle are using more energy than they are producing and are hindering the health of the tree. Like the old saying says “Too much of a good thing can be bad.”
Tree Structure:
Over the years a trees life will prune it self’s of dying, diseased, infected and injured branches to maintain structure and health. The key words are “over the years,” the problem with these is there are new infections, diseases, and injuries occurring to trees at faster rate in the past years, or aren’t native to, the area and the tree(s) haven’t formed protection against them. Proper pruning practices will increase the survival and maintain the health to an extent, but there are many other factors in the urban environment that hinders a trees health and condition. How can I known as a consumer if the tree company owner is telling the truth about proper tree pruning practices? Proper tree pruning practices across the entire United States for all arborists and tree companies alike should follow the American National Standards Institute (ANSI) A300. ANSI A300 is the industry standards for properly pruning a tree that was created through a collective effort of research and field experience to promote healthy trees. When the ANSI A300 is followed along with an experienced arborist, tree climber or consultant the tree benefits. An experienced arborist, consultant or tree climber can evaluate a tree and explain the reasons for pruning and why to prune a tree certain way. This process is easier during the winter for the simple fact because the leaves aren’t on the tree. The tree structure is much more visible when the leaves are off the tree; example: damaged branch, crossers, cankers, animal damage, many more can be hidden by leaf cover. For more detailed information on proper pruning techniques check out our learning Center. This same idea of better visibility is also true for the person performing the work in your tree; the tree structure is more visible so the work can be done easier and more efficiently. Also, structural pruning will decrease the amount of weak attached branches, which in turns decreases storm damage, which decreases property damage. The removal of the branches allows for less leaves to be formed, allowing the wind to pass through the canopy decreasing a sail effect and decreases weight loads on the branches, in which helps the tree handle storms better causing less damage.
Insects & Disease:
This is sweet and simple right the point; during the winter diseases and insects are not active due to the cold temperatures. The tree can heal its wounds from the pruning throughout the winter and spring and get a head start before the insects and diseases come back.