Save your garden from salt damage

(Jan 28, 2008) As we start to slip-slide our way through winter, keeping our walkways free of ice becomes important. But you need to protect your garden.

NaCl: the bad guy
Cheap and plentiful, rock salt (a.k.a. sodium chloride or NaCl) is the number one choice for tackling ice. Canada uses about five million tonnes of rock salt each year, most of which ends up in our lakes and rivers. Ecosystems adjacent to salted roads are often affected adversely by rock salt: plants are damaged or killed, water and soil is contaminated and in severe cases wildlife can become ill or die.

Salt can damage your lawns and gardens so you want to minimize its use.

Sand: a better option
Once the temperature dips below -9° Celsius (15° Fahrenheit) salt is unable to penetrate the now-solid water to start the dissolving process. Sand is often used in the bitter cold to increase traction and will not harm your garden. But you have to clean it up properly in the spring since it can easily clog drains and sewers. It also easily absorbs contaminants like oil and chemicals, carrying them into the water with the spring thaw.

Few choices and lots of confusion
Alternatives to salt are still hard to find for homeowners. There are a variety of synthetic de-icers, some more eco-friendly than others. The greener the product, the more expensive it will be. Most ice melters are a combination of salt combined with five other common materials:

Calcium Chloride (CaC12): less harmful to vegetation but corrosive to metal and can leave a residue on carpets, shoes and is harmful to pets' paws. Three times more expensive than salt but you need a third less. Works up to - 31° C/ - 25° F.

Potassium Acetate (KC2H3O2): the most biodegradable of all the de-icers, non-corrosive and safe for steel, but also lowers oxygen levels in water. Eight times more expensive than salt and can be hard to find. Works to -59° C/-75°F.

Calcium Magnesium Acetate (CMA): this dolomitic limestone and acetic acid is salt-free and biodegradable. Less damaging to plants but is 20 times more expensive than rock salt and only works to -3.89° C/ 25° F.

Magnesium Chloride: corrosive to metal and must be used precisely as it attracts moisture from the air and make the pavement wet if too much is used. Twice as expensive as salt and you will need to use twice as much. Works to -25° C/- 13° F.

Urea (NH2CO NH2): less damaging that salt but can still burn your lawn and garden. It also causes massive algae blooms in local waterways and does not perform well below – 28° degrees C/ - 20° F. It should be avoided.

Pet friendly not water friendly
Both Ethylene Glycol and Propylene Glycol are often found in “pet friendly” de-icers but are very toxic to all aquatic life and plants. Both should be avoided.

Consider the MET
Most "eco-friendly" products are a combination of chemicals, blended to maximum performance and minimum damage to the environment. The important thing to consider is the ice melt minimum effective temperature (MET). If you live in a more temperate climate where sub zero temperatures rarely occur, you don’t need an ice-melter with a MET capacity of -31° C/ -25 ° F.

Follow instructions and don’t use too much -- adding more does not make the snow melt any faster.

Greenest method
Physically removing as much snow as possible is the greenest way to deal with ice. De-icers are not formulated to melt through compacted snow or a build up of ice. The less ice there is, the less de-icer (or salt) you will need to use.

Anne Colvey is an environmental activist and journalist based in Quebec.



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