Repeated shoveling or blowing snow that contains de-icers onto nearby landscape plants will increase the likelihood of contact injury. Evergreens exposed to salts can show symptoms as early as February or March., including needle flecking, yellowing or browning, and twig dieback. Second, by repeated yearly applications the resulting build-up in adjacent soil may damage plant roots so they are unable to take up water. Plants symptoms include wilting even when soils are moist, an abnormal blue-green cast in the foliage, marginal leaf burn or needle tipburn, and general stunting or lack of vigor. Over time, some clay soils may have their structure changed by extremely high salt levels and become unable to support plant life.
Calcium chloride is the chemical most effective at extreme low temperatures.
It is also less likely to cause corrosion or plant damage when applied correctly. Avoid using rock salt whenever possible. Urea is also likely to cause pollution in run-off waters during the spring melt. De-icers should not be used to simply melt snow or ice. They should be used as an aid to mechanical removal.