Choosing Deicers That Are Friendly to Plants, Animals, and the Earth

While applying products to keep our walkways clear of snow and ice, it’s important to remember the nearby plant life. Deicing products, primarily composed of salt, can injure plant material, but is there a safer product to use around desirable vegetation? What about around pets? What about the run-off in our rivers and watershed?

• Salts can cause injury to trees, lawns, and shrubs
• Salt run-off can harm our groundwater
• Salts can corrode concrete
• Salts can do bodily harm to humans if handled improperly
• Salts are hard on the little paws of your four-legged friends

So you may be thinking salt is salt, right? No, not all salt is not the same. Think table salts (Sodium chloride) and Epsom Salt (magnesium sulfate). If you remember your days in chemistry, salts are combinations of negatively charged anions and positively charged cations. Examples are sodium chloride (table salt), potassium chloride (used as a fertilizer), and magnesium chloride (the one you see trucks spraying on our roads). The most problematic element in these salts is chloride, a corrosive ion that damages metal and concrete. Chloride is also toxic to plants.

Salt damages plants by dehydrating plant tissues, causing burns, or being toxic at high levels. While most plants have some tolerance to salt injury, repeated applications of deicing products during the winter can result in dieback or even death the following spring. Misapplications of deicers (i.e. dumping piles or using too much) can leach through the ground and into the water table or wash into the storm sewers, causing pollution. Before buying or using any product, read the label carefully and use only as directed.

Here are a few of the salt products you might run into while shopping:

Calcium magnesium acetate (CMA)
It has low corrosion potential, so it’s less damaging to cars, metals, sidewalks, and plants. Notice it’s not a chloride product, the “salt” comes from the calcium-magnesium mix and the acetate replaces the chloride. Plus, it’s biodegradable! Its ice-melting properties are equivalent to traditional deicers, but the cost may be 20-30 times as expensive as sodium chloride products. These are often touted as “pet friendly”. 

Magnesium chloride
Commonly referred to as “mag chloride”. Applied as a brine, it’s the most common product used on our roadways before storms because it lowers the freezing point of soon-to-arrive precipitation. It can melt ice down to -15° F, which is a nice benefit. If applied in moderate amounts, it’s relatively safe for plants and pets. Its corrosion potential is low, as is its pollutant possibilities.

Potassium chloride
It’s expensive and not as widely used as a deicer because of the rising costs of fertilizer. This works best when temperatures are above 15° F. Because it’s most commonly used as a fertilizer, it’s relatively safe to apply near plants.

Sodium chloride
It’s the most widely available and the cheapest. It doesn’t cause corrosion to concrete and melts ice best when temperatures are in the 20s. It is the most damaging to plant material. If you use this product, use it sparingly and in small amounts!

Before using any de-icing product, clear away as much snow and ice with a shovel as possible. If heavy snow is predicted, then try to shovel more frequently. Remember, deicing products are not meant to melt all snow and ice, but rather aid you in your removal efforts. If you want to avoid adding chemicals to your landscape, then consider using sand or kitty litter. While they don’t melt snow, they can provide traction in slippery spots. Sand and kitty litter are also safe for pets and plants and can be swept up when the snow melts.

If you use deicing products near vegetative areas, then use caution with potential salt build-up and consider a soil test in the spring.  If it’s an especially snowy year, you may consider rinsing the areas next spring with clean water. Try not to scoop snow laced with deicing products directly on top of plants, especially if they are sensitive. If you have the opportunity, consider planting more salt-tolerant plants near walkways and driveways. Here's a great publication on plant tolerance to salts.

For more information about sustainable gardening, contact your local University of Idaho Extension Office.