Sun Scald or Winter Injury
There have been several questions over the last few weeks about trees losing their bark along one side of the tree. If this issue shows up on the South or West side of the tree this is often caused by sun scald also known as winter injury. This issue poses a significant threat to many thin barked trees when they are young but often you might not know the damage was caused until years later. This issue is most common on maple, linden, honeylocust, cottonwood, birch, oak, peach, willow and ash. Sunscald refers to the process in which the living cells in the outer bark are damaged by the fluctuation in day to night temperatures during the winter. During the day the sun heats up the phloem and causes the sap to start to run on that side of the tree, then when the sun goes down and the temperature drops the sap freezes causing the phloem cells to burst from the expanding sap. Damage can result in discolored bark, bark cracking, sunken areas from lack of growth or the bark falling off to reveal the dead tissue within the damaged area. This damage can cause significant stress to the tree, especially during times of heat or drought, and can be a location for insects or diseases to enter the tree. Never cover the area with tar or any sealing substance as that can make things worse but you can wrap the trunk with light colored tree wrap. In many instances the damage will eventually heal however, it’s best to prevent sun scald when possible. In the fall, wrap the trunk with a light-colored tree wrap to help protect the trunk and lower branches from the temperature extremes. You can also use a plastic tree guard around the trunk to help deflect the sunlight. Wrap the tree for the first two to three winters to keep the trunk safe till the bark starts to thicken. It’s also been found that drought stressed trees tend to be more susceptible to sunscald so try to water the trees through the winter to help reduce the chances of having issues. We are getting close to time to wrap the young trees for the winter so anytime in the next few weeks would be the ideal time to protect your trees.
