“What do you recommend for deicing sidewalks?” was a recent question to AnswerLine. Most deicing products readily available on the market contain salt compounds known as magnesium chloride (used as a liquid on roads), sodium chloride (table salt), calcium chloride, and potassium chloride (fertilizer). Each winter these materials are applied to sidewalks, driveways, and steps to prevent slipping and falling. However, they are often applied without regard to the substance, application, or the damage that they may cause to the home, property, environment, pets, and nearby plants.
As for mentioned, deicing products are primarily comprised of salt. And just like household salt, all salts are not the same. Salts can cause injury to trees, lawns, and shrubs, corrode metal and concrete, and even do bodily harm to pets and humans. The most problematic element in any of the deicing products is the chloride; it causes corrosion and is toxic to plants.
The University of Maryland offers some great information on deicers in their help sheet, Melting Ice Safely. While this is an older publication (1998), there is good information on how deicers work and how to use them effectively and safely. On the second page of the publication, there is a table comparing the fore-mentioned products along with their effectiveness, corrosiveness, and potential harmfulness to plants.
A more recent product, calcium magnesium acetate (CMA), contains no chloride and is less damaging to cars, metals, and concrete and less toxic to plants. It is also said to be biodegradable and pet and wildlife friendly. It works very much like the traditional ‘chloride’ products to melt ice. The big downside is the cost.
If you want to avoid deicing products, consider using sand, kitty litter, or chicken grit. While these products won’t melt snow, they will provide traction in slippery spots. Sand and kitty litter are safe for pets and plants and can be swept up when the snow melts. (Chicken grit may be too sharp for the paws of some pets but will not harm plants.) Boots or shoes traversing any of these products should be removed upon entering a home as they could scratch floors.
Should the landscape fall victim to deicing, a recent article published by Reiman Gardens suggests flushing the area around the plant roots in the spring with water to leech out the salts.
The best advice is to know something about the substance (salts used in the product), consider the application, and then READ AND FOLLOW the manufacturer’s directions for applying the product to minimize damage to property and landscape. And if possible, apply even less than is recommended. Deicing products are not meant to replace shoveling or to melt all snow and ice, but to aid in removal efforts to prevent slipping and falling.