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Wed, Feb. 19

Backyard Gardener: There are a number of products that can help melt ice in winter

Chemical de-icers are often salts. Of these, sodium chloride (table salt) is the cheapest and most common. Others are calcium chloride, magnesium chloride and potassium chloride. (Jeff Schalau/Courtesy)

Chemical de-icers are often salts. Of these, sodium chloride (table salt) is the cheapest and most common. Others are calcium chloride, magnesium chloride and potassium chloride. (Jeff Schalau/Courtesy)

Northern Arizona gets its fair share of snow and ice in winter, and de-icing compounds are a common way of enhancing safety and access.

On north and east exposures, mechanical removal alone is often inadequate when ice accumulates on sidewalks, driveways and road surfaces.

For these situations, there are a number of products that chemically melt ice or physically improve traction; however, use of these materials is not without direct and indirect costs.

These compounds can be expensive, and can damage vegetation, hardscaping, indoor carpet and flooring, vehicles and the environment.

Chemical de-icers are often salts. Of these, sodium chloride (table salt) is the cheapest and most common. Others are calcium chloride, magnesium chloride and potassium chloride.

Chemical de-icing works because solutions containing salt freeze at lower temperatures than pure water. Pure water freezes at 32 degrees F. Water with salt dissolved in it freezes at temperatures below 32 degrees F.

Once a de-icing compound is applied to a surface, it melts the ice, creating a brine solution with a freezing point lower than that of pure water. The process continues until all of the ice is melted, or the melt water dilutes the salt solution to a point where it refreezes.

Because many factors are involved, there is no one material that is ideal for every situation. Select a de-icing compound based on existing conditions such as temperature, the potential for damage and public safety.

Where possible, use de-icing salts in moderation and combine with other management practices such as mechanical removal to reduce the amount of chemical needed and any subsequent impact to the landscape.

Calcium, magnesium and potassium chlorides are slightly less harmful to plants than sodium chloride. All are highly corrosive and can cause significant damage to landscape plants. Hardscape can be damaged when metal corrodes or when saturated de-icer solutions are absorbed by rock, porous brick-or masonry causing a 10% to 20% expansion. Concrete can be formulated to be more resistant to scaling, and cracking caused by salts and metal can be painted with corrosion resistant paints.

Indoor surfaces are dulled and require more frequent cleaning where salts are used in adjacent outdoor areas. Sodium and potassium chloride salts are relatively easy to remove from floors and carpets. Calcium and magnesium chloride salts, however, leave a greasy film and require wet cleaning with detergents to remove the residue.

Abrasives such as sand, cinders and ash have relatively few impacts on the environment or plants. These materials do not melt ice but improve traction on slippery surfaces. The disadvantage of these materials is that they accumulate in the landscape, and may require frequent removal or create dust problems when they dry later in the year after deicing season.

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.

Each de-icer has advantages and disadvantages. Planning a combined chemical and mechanical approach to snow and ice control can often minimize the impacts of de-icer compounds to plants in the landscape.

Use the following suggestions as you formulate your approach to de-icing. Use more mechanical removal. The more snow and ice present, the more de-icing compound is needed for melting. Reduced amounts can be used if large accumulations of snow and ice are removed first. The cost of labor for physical removal may be offset by savings in reduced damage to the landscape.

If possible, select abrasives that can be incorporated into the landscape to reduce the need for removal after the de-icing season.

Use de-icing compounds with minimal effects on plants. If possible, plant salt- tolerant vegetation in areas receiving large amounts of de-icing salt, or as a barrier between salt-sensitive vegetation and the site of de-icer application. Locate salt-sensitive plants away from the site of de-icer application and splash. Use hardscaping (gutters, barriers) to channel de-icing solutions away from planting areas.

When removing snow containing de-icer residues, do not pile on or near salt sensitive plants. Irrigate areas where de-icing compounds were used heavily in spring to leach accumulated salts from the root zone of plants.

You can follow the Backyard Gardener on Twitter – use the link on the BYG website. http://cals.arizona.edu/yavapai/anr/hort/byg/.

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