Chemical de-icers will help remove ice, but can also cause damage to the surrounding environment. Over application of chemical de-icers can shorten the life span of concrete surfaces, corrode metal railings, pollute streams and lakes through run-off water, damage soils and stunt or kill plants adjacent to de-iced areas. Manual snow-removal followed by the application of an abrasive such as damp sand or kitty litter to create traction can keep sidewalks safe without the problems associated with de-icers. Using de-icers wisely, or replacing them with manual removal and abrasives, can minimize the potential for damage while keeping steps and sidewalks safe.

Most de-icing chemicals are technically "salts" that work by lowering the freezing point of water below 32° F. Salts can damage plants in two ways:

First, by direct contact with snowmelt containing de-icers or in salt spray from roadways. Repeated shoveling or blowing snow that contains de-icers onto nearby landscape plants will increase the likelihood of contact injury. Direct contact can cause bud death and twig dieback resulting in the growth of twig clusters known as "witches brooms." 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. Well-drained soils can be watered heavily to leach some of the excess salts out, but this will not work with fine-textured clay soils or soils with inadequate drainage.

De-icing chemicals vary in their effectiveness as de-icers and their potential for damage.

De-icer Information
Common chemicals for de-icing	Lowest effective temperature	Damage to plants	Soil damage	Water pollutant	Damage to concrete/metals
Common salt	+15°F	High	High	Yes	Yes
Calcium chloride	-20°F	Medium	Medium	Yes	Yes
Calcium magnesium acetate	+15°F	Low	Low	No	No
Urea	+15°F	Medium	Low	Yes	Yes

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, (lawn fertilizer), can burn plants and lawns if too much is applied. 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. All de-icers need to be used after shoveling and sweeping has removed as much snow and ice as possible and after the threat of additional snowfall has ended. The de-icer will melt down to the surface and allow manual removal of the final layer of snow or ice. De-icers should be mixed with an abrasive such as sand or kitty litter so that the amount of chemical used can be reduced and the abrasive can provide traction. Spread the mix evenly and clean up any clumps or spills. Avoid shoveling snow that contains de-icers directly onto plants. Whenever possible, remove snow and ice manually and then spread an abrasive.

Advance landscape planning can minimize plant damage from de-icers. Landscape plants differ in their tolerance to salt exposure; some are highly sensitive while others are more tolerant. When planning new landscapes, or redesigning existing ones, use relatively salt tolerant plant species in areas adjacent to de-icing locations.

Sensitive		More Tolerant
Pinus strobus	Eastern White Pine	Gleditsia triacanthos	Honeylocust
Taxus spp	Yew	Juniperus chinensis  'Pfitzerana'	Pfitzer Juniper
Thuja occidentalis	American Arborvitae
Berberis thunbergii	Japanese Barberry	Ribes alpinum	Alpine Currant
Cornus spp	Dogwood	Philadelphus  spp.	Mock Orange
Spirea spp	Spirea	Potentilla fruticosa	Bush Cinquefoil
Rhododendron spp	Rhododendron/Azalea	Symphoricarpos	Common Snowberry

Make sure areas receiving snow and de-icer have good drainage so a thorough watering in the spring can help flush the excess salts. Plant tolerance is increased if the soil is rich in organic matter. Soils can be amended with organic matter such as compost or peat moss. Incorporating Gypsum into the soil may also help offset some of the negative effects of de-icing salts. Incorporate 10 to 20 pounds of gypsum per hundred square feet prior to planting in salt exposure areas.