Tree Top-ics: Pruning for health and structure

V.J. Comai
V.J. Comai

By V.J. Comai
Trees are dynamic living organisms that come in a variety of shapes and sizes and can live for decades or even centuries. In the urban landscape, their benefits are well documented as they provide cooling shade in summer, food for people and wildlife, reduction of storm water runoff, increased property values, and carbon sequestration, to name a few, all while adding to the aesthetic beauty of our communities and home landscapes.

Trees in the urban landscape require periodic maintenance if they are to continue to thrive and provide benefits for years to come. Aside from proper planting, diligent care during the establishment period, and selecting the right tree for the right location, proper pruning, especially in the first twenty years, can help to ensure the health and structural integrity of our trees as they grow and mature.

As an arborist, I evaluate the health and potential risk of mature trees on both commercial and residential properties daily. I am often confronted with situations where property owners are faced with the costly removal of a large tree that poses a significant threat of failure, resulting in likely damage, simply because no preventative structural pruning was performed on the tree as it was developing and maturing. While even the most structurally sound trees can fail in extreme weather events, most partial or total tree failures that occur during the average storm do so at the point of structural defects in the tree that never would have developed if a few critical pruning cuts were made at an early age.

Such early pruning can mitigate the development of codominant stems, multiple trunks of similar size that lead to weak junctions prone to splitting under heavy wind or significant snow and ice loads. Proper and more frequent pruning of fruit trees can help to ensure good branch structure that can withstand the weight of heavy fruiting, which can lead to branch-failure. Early pruning can also eliminate crossing and closely spaced branches that will result in problems down the road. Pruning of mature deciduous trees is primarily done to remove larger dead or diseased wood, thus serving to reduce hazards from falling debris.

More frequent pruning of ornamental flowering trees such as crabapples, or yearly pruning of fruit trees can improve flowering and fruit production by allowing for better air flow and light penetration while helping to reduce the incidence of diseases that affect fruit quality.

The removal of dead, diseased, or damaged limbs can be done at any time of year. But significant removal of live growth is best to leave until the dormant months and can be completed up until late winter before buds begin to swell. As a rule, no more than 20-25% of the total live wood in a tree should be removed in one season. Therefore, large old flowering crabapples or fruit trees that have been long neglected may require restoration over a period of a few years. Most other deciduous trees, once they have received a good structural pruning, will likely not need additional pruning for several years depending on their stage of maturity and rate of growth.

Proper pruning requires significant training, and improper pruning can do more harm than good. Understanding basic tree biology and the species of tree you are pruning are critical. Take some time to learn and understand the basics and look to reputable sources for sound advice. Avoid potentially dangerous situations and leave any pruning that you can’t complete with your feet on the ground to a certified professional. Your trees will benefit from proper maintenance, which will serve to ensure their health and structural integrity for years to come.

V.J. Comai is a resident of Charlotte and works as an arborist representative for Bartlett Tree Experts. For nearly 25 years he has managed the South Forty Nursery in Charlotte where he grew field produced trees and shrubs for the wholesale market. He is certified arborist with the International Society of Arboriculture, (ISA) a past president of Green Works, The Vermont Nursery and Landscape Association.

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