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Road in Winter
Salt and De-icers

January - February, 2006

Preservation issues dictate many aspects of Riverwoods life, and use of road salt is a primary example. Icy streets, driveways and sidewalks are dangerous, and as a result, most communities choose to apply de-icing salt. But de-icing salt (typically sodium chloride), which reaches plant-life through snow melt runoff and traffic spray, is poisonous to plants and animals, erodes concrete and corrodes aluminum and other metals.

While all vegetation is susceptible to injury from exposure to salt, some species are particularly vulnerable. Here is a chart showing plant species particularly at risk of salt injury:

Category of Plant Species
Deciduous Trees Hickory, Oak, Maple
Evergreen Trees Pine, Hemlock, Spruce, Firs
Shrubs Dogwood, Redbud, Hawthorn, Viburnum
Grasses Lawns, Native and Decorative Grass

Damage to plant life is exhibited in a number of ways. Salt deposited on small branches and buds causes desiccation and burn, and on evergreens, deposited salt causes browning or yellowing of needles. Salt that migrates into the soil and groundwater creates a toxic solution that poisons plants through their root systems. Even minimal salt induced plant poisoning is noticeable in browning along leaf edges, stunted growth, fewer and smaller leaves, and flower and fruit reduction in the following growing season. Heavy concentrations of salt will kill even large plants.

Alternative de-icers are available. They include calcium chloride, calcium magnesium acetate, urea, and sand. Here is a comparison chart.

Material Use Cost Environmental Impact
Sodium chloride
(rock salt)		 To +15° F Low Highly toxic
Calcium chloride To -25° F Medium Medium toxicity
Urea To +25° F Medium-high Medium toxicity
Magnesium chloride To -15° F Medium Medium to Low toxicity
Calcium magnesium acetate To +25° F Very low Low toxicity
Sand For traction only Very low No toxicity
Kitty Litter For traction only, but gets gooey and messy when wet Very low No toxicity

Toxicity is a function not only of the type of material used, but also the amount. The recommended application for rock salt is a handful per square yard treated. Using more salt will not speed the melting process. The recommended application for calcium chloride is less – about a handful for every three square yards.

Usage Guidelines

  • Reduce the amount of chloride-containing salt used by mixing it with sand.
  • Clear snow before applying a de-icer, to increase effectiveness and reduce usage.
  • Avoid putting salt-laden snow on top of the root zones of plants.
  • Protect especially sensitive species from damage from salt spray by using barrier fences (e.g., of burlap) to shield them.
  • Alter drainage patterns to avoid accumulation of salt run off near plants.
  • Check the list of salt tolerant trees and shrubs (e.g., the Morton Arboretum Tree and Shrub Handbook). Select those plants for trouble spots.
  • Apply pelletized gypsum on grass and plants near sidewalks and driveways to neutralize the effects of salt.
  • Consider the impact on animals. Animals that walk on areas that have been de-iced are prone to dry, chapped and irritated paws. The pain may cause them to lick their paws, injesting the de-icer. It is best to wash your pet’s paws when it comes in from outside.