Winter injury has been a common problem on young and even mature trees in Central Kansas over the last several seasons. Winter tree injuries are a frustrating problem for homeowners-especially because the damage may not be seen or noticed until much later the following year. Many of these injuries have come in the form of sunscald/ freeze injury or winter desiccation (drying) damage. New and young trees and evergreens are the most susceptible to winter injuries and action can be taken now to prevent more of this type of damage in 2023.
Sunscald is a term used to describe the cracking and splitting of tree bark due to high heating and/or cooling at a rapid rate. Sunscald can occur both in the extreme heat of summer and during the winter. A typical winter day in Kansas may be sunny and 40-50 degrees. The high intensity sunlight occurs at lower angles during the winter and this heats up the south and southwest side of tree trunks. The heat can cause cells to come out of dormancy and become active. Once the sun sets or the weather quickly turns below freezing the cells and conductive tissue are killed.
This type of injury initially appears as sunken and discolored bark and later the bark will crack, split, and fall off the tree in patches. Thin barked trees are especially prone to sunscald. Maples, fruit trees, willows, lindens, honey locust, some oaks and many other trees can easily be damaged, especially when young.
What to do
New and young trees can be tree wrapped to help reduce winter sunscald damage. There are many commercial tree wraps and guards available. Some are made of corrugated plastic and can slip around the tree trunk while others are a crepe paper material that is simply wrapped around the tree trunk. Trunks should be wrapped upward from the base of the tree to a point just above the lowest branches. When using paper wraps, overlapping of about 1/3 on each turn is recommended.
For winter protection, wrap trees from November through April (think Thanksgiving and Easter) to reduce exposure to direct sunlight and heat. Paper type wraps should be removed in spring to avoid pests that may get underneath. Trees should be wrapped/protected each winter until the bark becomes thick and corky. Another benefit or a tree wrap or guard is protection from the feeding of rabbits or small rodents that can cause extensive damage to the trunks of small trees during the winter.
Desiccation and freeze injury
Desiccation simply means drying out. A dry winter is very stressful on any tree, and especially on evergreens. All plants continue to transpire during the winter, and water conduction may be restricted by the freezing of plant tissue or frozen soil. When water loss through transpiration isn’t replaced, winter drying kills portions of the plant. Many times winter desiccation is worse on the side of the plant facing the prevailing wind.
Freeze injury can occur even when moisture in the soil is adequate and is usually the result of extreme temperature swings during mid-winter. In January, Kansas often experiences stretches of warm mild days that may be enough to cause trees to begin losing their acclimatization to the cold. If extreme cold returns after a stretch of mid-winter mild weather, winter injury is much more likely.
What to do
Prevent desiccation by making sure that trees and woody plants enter winter with good soil moisture. Current soil moisture conditions range from moderate to extreme drought in most areas of Kansas and this needs to be monitored throughout the winter especially on young trees and evergreens. If conditions stay dry, a mid-winter watering will be of great benefit. Trees and shrubs can be watered when needed during the winter on days when the temperature is at least 40 degrees and the soil isn’t frozen.