The best way to keep surfaces free of snow and ice is to sweep or shovel them away. Alternatives to chemical ice melts include clean, non-clumping kitty litter, saw dust, coffee grounds or sand.
Salt damaged yews
Photo courtesy Purdue University
Five chemicals are used to make deicers: calcium chloride, sodium chloride or rock salt, potassium chloride, urea and calcium magnesium acetate. Usually deicers are a mixture of ingredients.
Boxwood dieback from winter cold and salt damage.
Photo courtesy Purdue University/Gail Ruhl
The chlorides are chemical salts and require caution when using them around plants, concrete, brick and other hard surfaces. These chemicals can leach into the soil and damage plants. Or, they can damage surfaces when not used properly. Rock salt also can change the chemical balance of the soil and can accumulate to toxic levels. Salts sprayed from road traffic also can damage plants. Salt spray that lands on branches or stems and evergreens may cause excessive drying. To protect roadside plants, erect a shield out of burlap or other material.
Some deicers are mixed with urea, a fertilizer. However, it can contaminate the soil and surface water runoff with nitrates. If overused, urea can damage plants and corrode metals.
Calcium magnesium acetate is considered the most environmentally friendly deicer and the safest for use around plants, concrete and other hard surfaces. It is made from dolomitic limestone and acetic acid, the main compound in vinegar. Unlike other materials, CMA does not form a salt brine or slush. Instead, it prevents snow particles from sticking to each other on surfaces. This product is not considered hazardous to plants or concrete, however, it works more slowly and is usually more expensive than other deicers.