Winter is on its way; its time to get your trees ready. While splitting tree bark will typically not kill a tree, it will reduce the value and make it unsalable if severe enough. Luckily, frost cracking is a very easy injury to prevent.
In the winter months, sudden temperature changes can cause the water within the vascular tissues of tree trunks to freeze and expand. This results in splitting of the bark. This occurrence is often called southwest injury or frost cracking. The splits usually occur on the lower southwest portion of the trunks where the warm afternoon sun has the most exposure and the better chance to heat up the trunk during the day. However, these cracks don’t just appear out of thin air. A pre-existing wound is required for the tree to suffer from frost cracking. Often, initial wounds are pruning injuries that can be prevented. The most susceptible trees are species that have thin bark, making it easier for the temperature to manipulate and crack it.
Trees Most Susceptible to Southwest Injury:
Maples, Eastern Redbuds, Apple, Crabapple, London Plane, Oak, Horsechestnut, Walnut, Willow, and Linden
The best method of prevention is avoiding wounding young trees when pruning or performing other types of day-to-day maintenance. However, this isn’t always feasible, especially if you have a lot of trees to maintain. To more confidently prevent southwest injury, the trunks of young trees should be protected with tree guards or tree wraps. These are easy to purchase online, at your local garden center, or any hardware store. For the best results, make sure you purchase white tree wraps or guards. The white color will assist in reflecting the sun and reduce the temperature increase during the day. This will in turn close the gap between the temperature difference from day to night, since the temperature during the day will be lowered. It is important to remember to remove the tree wraps and guards when winter comes to an end. Leaving the wraps or guards on the tree for longer than one season can result in insect or moisture damage. Another less common option is painting the trunks of your trees white. Since this method is less aesthetically pleasing and time consuming, it is not used as often.
Additionally, poor tree health can make a tree more susceptible to southwest injury. A tree suffering from herbicide injury, a pest infestation, or disease is the perfect candidate for southwest injury. If a tree is in good health, it can often fight off frost cracking and heal the wound itself without any human intervention. It is important to make sure your tree is in good health before going into the tough winter months. Irrigating the tree when it becomes dry until the ground freezes is a good practice to get in the habit of as well as managing pest and disease issues as they occur.
The best way to prevent frost cracking is to know how and why it occurs. Once you understand the physiological process, you can better implement effective solutions. Southwest injury can remain with a tree for its entire lifetime, so it’s best to protect them now before its too late.