Question. Are deicing salts bad for my plants?
Answer. While deicing salts are important tools, the runoff from treated pavement contains dissolved salts that can injure and even lead to decline and death of many trees and other vegetation.
Most damage occurs within 30 feet of a roadway or parking lot. Along high-speed roads, salt may also drift onto vegetation, up to 60 feet or more away. Salt spray commonly causes bud death and twig dieback in deciduous plants. This may result in a type of ‘witches’-broom’, tuft-like growths from braches facing the road. Evergreens may exhibit moderate to extreme needle browning, beginning with the tips of needles and twigs facing the road. This becomes evident in late February or early March and intensifies through spring and summer. Other symptoms of salt injury include stunted leaves, heavy seed load, twig and branch dieback, leaf scorch, and premature leaf drop.
In residential areas, trees, shrubs, and lawns are more often damaged by salts accumulating in the soil. Soil salt damage often becomes evident late in the summer during periods of hot, dry weather. Symptoms may include abnormal foliage color, needle tipburn, marginal leaf burn, reduction in flower or fruit size, stunting, premature fall color and a general decline in health. Unfortunately diagnosing salt injury can be difficult as symptoms are similar to injury caused by other stresses. Soil and tissue analysis can verify salt injury.
Limit applications to high-risk locations (i.e., steps, walkways). Reduce the quantity applied by mixing the salt with abrasives such as sand or kitty litter. Deicing salts such as calcium chloride and calcium magnesium acetate are less damaging that sodium chloride.
Kelly R. Jackson is the Christian County Extension Agent for horticulture. He can be reached at 270-886-6328 or visit Christian County Horticulture online at www.christiancountyextension.com.