Deicers

Deicers

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Q: What kind of deicer should I use that won't hurt my plants? I used some deicer that I happened to have on hand and it turned my brick white. Is that bad?

A: The white color is a film left behind from the salts in the deicer. It's not permanent and will wash away. If you're looking for deicers that will have less impact on plants, we recommend staying away from rock salt and using windshield washer fluid or a product that's labeled as plant-friendly. Windshield washer fluid has alcohol that will lower the freezing temperature of water, though it's better at melting ice than preventing it. In an emergency you could also use fertilizer (yes, fertilizer!). If you use a fertilizer, try to use one that's low-strength and high in potassium. It's the potassium that does the deicing. Don't make it a regular habit though, the excess fertilizer will eventually make its way to the bay.

Whatever you use, be sure not to use too much. One mistake people sometimes make with deicer is to use too much. Don't expect deicer to completely melt ice. Instead, use the amount indicated in the directions and shovel away the ice once it has become slushy or broken up.

One concern with deicers is damage to concrete. Most commonly used deicers don't directly attack concrete, it's the repeated freezing and thawing that causes spalling. This problem will be most evident on poor quality concrete with little or no entrained air. If you think your concrete might be susceptible, calcium chloride might be your best choice, it works at lower temperatures, reducing the number of freeze-thaw cycles.

Here's some additional information from the University of Missouri Extension:

There are five chemicals commonly used as deicers. They may be used alone or combined with other materials to enhance their performance.

  • Calcium chloride often works better than other deicing salts, especially at lower temperatures, because it gives off heat as it melts. It also will not leave behind a residue unless mixed with other chemicals.
  • Sodium chloride, or rock salt, is relatively inexpensive, but it can burn plants and corrode metal and concrete. It was first used as a road deicer in the 1940s. 
  • Potassium chloride is a naturally-occurring material that is also used as a fertilizer and food salt substitute. Its high salt index has the potential to burn foliage and inhibit rooting. 
  • Urea is made from ammonia and carbon dioxide and is used primarily as a nitrogen-based fertilizer. It is less likely to burn foliage than does potassium chloride. 
  • Calcium magnesium acetate (CMA) is a new, salt-free melting agent. It is made from dolomitic limestone and acetic acid (the main compound of vinegar). This material has little impact on plants and animals, is a good alternative for environmentally-sensitive areas.

For locations where chemical deicers aren't appropriate, sand or cat litter can provide some traction but will not melt snow and ice.

-Phillip Merritt


Hertzler & George

 is a design, build and maintenance firm in Williamsburg, Virginia dedicated to the development of extraordinary gardens and properties.

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