MANHATTAN, Kan. – De-icer does not provide the traction needed to walk safely on slick sidewalks.
“The traditional way to create traction is to scatter cinders or sand. But, some homeowners are now using natural-clay kitty litter instead. Others are feeding the birds while providing traction by sprinkling cracked corn or bird seed,” said Ward Upham, horticulturist with Kansas State University Research and Extension.
Each of these options has its pros and cons, Upham said. But, none works as well as getting out the shovel and removing snow and ice as soon as a winter storm subsides.
De-icer can be helpful as part of that removal -- particularly if applied before the storm or after the snow’s been moved out of the way. De-icers’ basic purpose is simply to “break” the bond between ice and pavement, usually by causing the ice to melt, he explained. In general, the thinner and newer the ice, the better de-icers work.
“You need to follow up with a traction provider only if you leave slick spots or slush behind – either of which can make walking hazardous,” Upham said. “If so, you may want to make people leave their shoes at the front door.”
Slush itself contains ice, but if it’s loaded with de-icer, it also may be rather slimy. In turn, when the slimy stuff comes indoors on shoes, it may create interesting spots that dry and leave chemical residues.
Of course, walkers will track traction-adding materials, as well, Upham said. And, once indoors, cinders can stain fabrics. Sand can be difficult to clean up completely, plus it can abrade rugs and floors. Scattered, damp kitty litter can be a sticky mess.
How big a nuisance that becomes, however, relates to a second problem with traction-providing materials: Homeowners tend to forget to sweep up and throw them away as soon as the current need for them is gone.
“When you leave such materials on your sidewalk, they end up in one of two places,” he said. “They get stuck in the edges of your landscape. Or, snow melt and rain take them into your street’s gutter, down into the storm drain system and out to a nearby natural body of water. There, they become a space-filling pollutant.”
The materials stuck in landscape edges can be a problem, too. Sand can build up to create a layer that interferes with rooting or, if mixed with clay soils, can create dirt that’s a lot like concrete. Adding cinders will raise the soil’s pH -- which may already be high where limestone abounds. Bird seed can sprout into “out-of-place plants,” the very definition for weeds.
“Mistakenly using de-icer to provide traction can be worse, though,” Upham warned. “You don’t want to use any more de-icer than absolutely necessary around your landscape. Limited use of any of these products should cause little injury. But a buildup of de-icer chemicals can injure the plants and grass growing along walks and driveways. It also can pit concrete – an impact you may not notice until months later.”
Match De-icer Choice to Conditions, Concerns
MANHATTAN, Kan. – De-icer products seem to tempt homeowners to adopt the approach of “if some is good, more should be better.” That excess use is what has given de-icers a bad name for injuring plants and damaging concrete.
“When homeowners think they need to apply ‘extra,’ the real problem may be that they don’t know the limits of the product they’re using. For example, their product of choice may not work well when the temperature is below 20 degrees,” said Ward Upham, horticulturist with Kansas State University Research and Extension.
To help homeowners make more informed decisions, Upham has summarized the characteristics of the five major ingredients used in chemical de-icers:
* Calcium magnesium acetate (CMA) – an acceptably “green” and typically more costly product made from dolomitic limestone and acetic acid (the principal compound of vinegar). Its performance decreases as the temperature drops below 20 degrees. But, CMA does not form a slimy brine as some other de-icers do. It helps prevent snow particles from sticking to each other or the sidewalk/road surface. CMA also has little effect on plant growth or concrete surfaces.
* Calcium chloride – recent decades’ traditional product. It will melt ice to about 25 degrees below zero (-25F). It gets to work fairly quickly, because it attracts its own “solvent” and then gives off heat as it reacts to the water. It does form a slippery, slimy surface on concrete and other hard walkways, but probably won’t hurt plants unless homeowners apply excessive amounts.
* Sodium chloride (rock salt) – the oldest, cheapest option. It remains effective down to about 12 degrees. Whether splashed or melted onto nearby surfaces, it can seriously damage not only plants but also metals and soils (i.e., “sow salt”). On concrete, it increases the impacts of winter’s freeze-thaw cycles, so can be particularly damaging for new pads and sidewalks.
* Potassium chloride – a naturally occurring material also used as a food-salt substitute and a fertilizer. It can melt ice when temperatures are in the teens. It’s not widely available as a de-icer ingredient, however, because the compound’s high salt index can lead to serious plant injury, above and below ground.
* Urea (carbonyl diamide) – a fertilizer sometimes used to melt ice in temperatures down to 21 degrees. Urea is only about one-tenth as corrosive as sodium chloride. It’s less likely to burn plants than potassium chloride. But, it can contaminate ground and surface water supplies with nitrates.
“Obviously, there is no perfect choice. The key is to match the product you use to your current needs, so you’re never tempted to apply more than recommended,” Upham said. “Of course, whenever feasible, an even better option is simply to shovel snow early enough and well enough that using a de-icer isn’t necessary.
“As its name implies: A de-icer can help you clear away ice. It is not a snow shovel substitute.”