As temperatures fluctuate, trees and shrubs can be damaged by freezing and thawing when there are very cold nights followed by warmer sunny days. Most materials shrink as they get colder and expand as they warm. The same is true for soil and for the bark of trees. This is what leads to two common cold-related injuries: frost heaving and winter bark cracking (splitting).
Frost heaving occurs when the upper layers of soil expand during the day as sunlight warms and thaws the surface, and then freezes and shrinks at night when the temperature drops. This constant cycle of expansion and contraction causes the soil to move and crack. This movement can break roots, or can push entire shrubs out of the soil (and also causes pot holes). This type of damage is most common on shrubs and recently planted small trees.
The second way in which expansion and contraction due to temperature fluctuations damages trees is a phenomenon known as frost cracking. This occurs when the bark expands as it warms during the day. Usually the southwest side of the bark warms the fastest and damage is most commonly seen on the south or southwest side. When the sun sets and the temperature drops, the outer layer cools and contracts faster than other portions, resulting in vertical cracking. These cracks can later be colonized by decay fungi, or serve as an entry point for various borer insects.
Understanding how temperature can impact your trees can help you identify potential issues before they become serious.
Fall is a great time to plant new trees in your landscape. With cooling temperatures and increased rain, there is less drying out of newly transplanted trees. This increases the likelihood of tree survival. Root growth increases in the fall, so tree stability is improved, and more water and nutrients can be absorbed to prepare for next spring’s growth spurt.
Be aware, though, that depending on your zone, certain trees including some maple, birch, beech and dogwood species are considered ‘fall planting hazards.’ These trees can more easily be damaged by cold winter temperatures and should not be planted now so be sure to research what works in your area.
New transplants should be mulched with wood chips or other organic material to insulate the soil and maintain soil moisture levels. Mulch should be applied from just off the trunk to the outer dripline whenever possible. If there is dry weather, irrigate the root zone deeply, but do not apply water directly to the trunk.
Regardless of where you live, winter brings with it colder and harsh weather. Winter storms and high winds can result in structural weaknesses in your trees including broken, bent or hanging limbs. Careful inspection of the trees and shrubs on your property can help prepare them for the months ahead.
Cabling trees having a weak “V” crotch is recommended. Pruning to eliminate any weakened branches is also a good practice. Any cracks or breaks should be inspected as these injuries frequently invite harmful insects and disease organisms in the spring. Finally, roots should be inspected carefully. Special attention should be given to leaning trees, which are subject to high wind loading (top heavy) and may be susceptible to root failure.
REGULATING TREE GROWTH
Sometimes, frequent pruning is required to maintain tree size and prevent interference with structures and sidewalks. For trees that grow quickly, structural issues can also develop. In these cases, extra care is needed to maintain root-crown ratios and reduce the potential of trees toppling in windstorms. An alternative solution for these trees is growth regulators.
Tree growth regulators have been developed to slow the growth of woody plants. Applied to the soil immediately adjacent to the stem, the growth regulator is absorbed and translocated throughout the crown. While the products don’t stop growth, they do slow growth significantly for a period of approximately two years. In addition, treated plants demand less water because of the growth regulation. Growth regulators can be applied throughout the year, and are an excellent way to manage fast growing trees.
Tree Artisans 3415 Cedarlawn Dr. Colorado Springs, CO 80918 www.treeartisans.com 719.822.6733