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!
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.
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