April 2014 Plant Disease Update
During late winter and early spring leaf scorch symptoms are noticeable on many evergreen plants. Leaf scorch is particularly apparent on broadleaf evergreens, such as Southern magnolia, holly, and cherrylaurel, but it can also occur on conifers, such as arborvitae. These symptoms are not caused by a disease, but by winter desiccation.
Evergreens continue to lose water through their leaves during the winter, and at higher rates when exposed to sun and wind. Roots cannot replenish water when the ground is frozen and leaves desiccate as a result of this water deficit. This year symptoms of winter desiccation are severe due to very cold and sustained winter temperatures, along with high winds from many winter storms. Plants in exposed, windy sites experience more desiccation and recently planted evergreens may be more sensitive because of inadequate root establishment.
Growers should not be overly concerned about winter desiccation. Severely injured leaves should drop when growth resumes in the spring and plants should eventually green up. When new growth appears, dead branch tips can be identified and pruned back to healthy tissue. To minimize winter desiccation, plant broadleaf evergreens in locations where they will not be exposed to prevailing winds. Ensure plants receive adequate water during the growing season and irrigate plants deeply before the ground freezes if conditions have been dry. Mulch also helps plants conserve soil moisture. Anti-desiccant products are available, but not practical in most situations.