Written by Fred Hoppe, Board Certified Master Arborist WI-0556B, and ISA Qualified Tree Risk Assessor; and John Sepulveda, Certified Arborist WI-1454A
Many urban trees are lost during the summer storm season each year due to lightning and high winds. However, trees damaged by storms are often not a complete loss. Trees can respond to injuries and to infection by a pest, fungus or bacteria to recover good health. And with some strategic pruning, good branch structure and canopy formation can be redeveloped.
Corrective Pruning
Storm damage can be traumatic to a tree. The loss of portions of the canopy can make the tree more unbalanced, thus more likely to have future damage. Large wounds are likely to develop into decay pockets and can weaken the tree.
After the clean up of broken or fallen limbs, the next important thing to do is to inspect the structure of the remaining tree. Often corrective pruning can be done to the tree to minimize future problems for the tree. Stubs or tears are removed with proper flat cuts that leave less surface area for decay to develop. Strained, cracked or damaged limbs are removed. Storm events can leave a tree with weak structure and limbs or stems more prone to exposure to wind. A certified arborist can review the tree and determine if pruning other parts of the tree will make the tree stouter and better able to withstand nature’s fury.
Trees with storm damage have newly opened areas within their canopy. New branches use this to their advantage and start to grow and fill in these new areas of sunlight. It’s important to observe how the canopy fills in and make sure these new branches are growing with proper structure with well-spaced, strong branch attachments. It is likely that a few years after a storm event a tree will need structural pruning to make sure the new canopy is strong and healthy.
Compartmentalization of Decay in Trees
When they are injured or under attack by infection, trees create physical and chemical barriers to stop the spread of infection throughout the rest of their tissues. This system is known as compartmentalization of decay in trees (CODIT).
After injury the tree will release hormones to begin the process of slowing down the spread of decay. It occurs in four sections known as the reaction zone:
Wall 1, the weakest of the walls, begins with plugging the pores on the top and bottoms of the cells to prevent the vertical movement of infection up and down the vascular system.
Wall 2, also a weak defense, prevents the spread of decay to more interior rings of the tree.
Wall 3 forms in the cells of the tree which are arranged radially, preventing the spread of decay around the tree to the sides of the site of the wound. Wall 3 is fairly strong as it has a lot of starches and stores of photosynthates.
Wall 4 is the final and strongest barrier. It surrounds part or all of the tree’s wound at the outermost ring to stop the outward growth of decay. Wall 4 will stay for the life of the tree and can be seen in hollow trees as the last layer of wood before the open pit of the trunk. The resulting wood that forms after Wall 4 will often fold over, creating a donut of successive tissue that continues until the wound is completely closed and new tissue can form in complete rings.
Helping Trees Recover With Plant Health Care
As certified arborists, preserving damaged trees is always something we will explore first. There are strategies we can use to help support them as they recover, such as:
Fertilization. Soil injection fertilization throughout the root zone with slow-release nutrients improves recovery from stress and promotes root and plant growth. This can lead to better growth to help fill the loss of sections of the canopy.
Growth Regulators. Growth regulators extend the life of trees by allowing the tree to redirect energy from canopy growth into defense mechanisms for increased resistance to insects and diseases, along with increases in fine fibrous absorbing roots. This treatment is often done to help promote wound healing and make the tree more resilient to future environmental stress such as drought, or another storm.
Storm damage can be a serious issue for a tree, but with the proper care a tree can recover. One of Hoppe Tree Service's certified arborists can inspect your damaged tree and determine the best course of action. Or better yet, inspect your tree before a storm occurs to determine if it is safe or if pruning or treatments should be performed to minimize the potential of damage.
Since 1972, Hoppe Tree Service has been taking care of people and their trees. Join us as we celebrate 50 years of service to great customers in southeastern Wisconsin.