Many young, smooth, thin-barked trees such as honey locusts, fruit trees, ashes, oaks, maples, lindens, and willows are susceptible to sunscald and bark cracks. Sunscald normally develops on the south or southwest side of the tree during late winter. Sunny, warm winter days may heat the bark to relatively high temperatures. Research done in Georgia has shown that the southwest side of the trunk of a peach tree can be 40 degrees warmer than shaded bark. This warming action can cause a loss of cold hardiness of the bark tissue resulting in cells becoming active. These cells then become susceptible to lethal freezing when the temperature drops at night. The damaged bark tissue becomes sunken and discolored in late spring. Damaged bark will eventually crack and slough off. Trees often recover but need TLC — especially watering during dry weather.
If you have seen this type of damage in previous years or fear you have susceptible trees, preventative measures are called for. Applying a light-colored tree wrap from the ground to the start of the first branches can protect young and/or recently planted trees. This should be done in October to November and removed the following March. Failure to remove the tree wrap in the spring can prove detrimental to the tree.
Lauren Fick is a Cottonwood Extension District Horticulture Agent. Hays Office: 785-628-9430. Great Bend Office: 620-793-1910.