Released Dec. 17, 2007
LAWRENCE, Kan. -- From a landscape plant’s viewpoint, the best way to deice a sidewalk, driveway or street is to use a shovel, blower or blade.
“Deicers are unregulated. Thus far, no ice- or snow-melting product is truly safe for the environment,” explained Jennifer Smith, horticulturist, Kansas State University Research and Extension.
Human safety has to come first, Smith added. But, humans can give the environment somewhat of a break by making informed choices as they decide how much and which deicer to use.
“Apply deicer only if ice remains after the shoveling’s done,” Smith advised. “Deicer isn’t needed on surfaces that are simply wet, unless you’re pre-treating because icy conditions are in the near-term forecast,.”
At that, the best approach is to apply deicer sparingly and check back later to see if more is needed, she said. Too much of a deicing agent can make some ice-melting products less effective. Many products also become less effective below 20 F, making a full application a waste of time and money
. “I’ve seen multiple places where the salted sidewalks were as white as the snow-covered ground nearby,” Smith said. “Even shoppers with less than practical shoes weren’t slipping on those salty crusts.
“But, you don’t need that amount of product to melt the snow. So, the walkers also were tracking leftover deicer everywhere. And, when the remaining deicer finally washes off, it will flow straight into nearby turf and landscape plants or into the storm drain system that leads to nearby streams and helps re-supply our groundwater.”
Although no deicer is harmless, some are better than others, the horticulturist said.
Sand and cinders, for example, aren’t toxic to plants, Smith said. But, they can pile up along curbs and on top of soil, where they can be difficult to remove. In most parts of Kansas, at least, they also can have a negative effect on the soil.
“Sand plus clay produces something very much like concrete,” she said. “Cinders raise soil’s pH, which already is high here in limestone country, thereby making it harder for roots to absorb nutrients.”
Fertilizer and urea are deicer alternatives that in their other “life” provide plant nutrients. In large amounts, however, they burn plants, Smith said.
The effects that commercial deicer products can have depends on their major active ingredient.
“You may have to turn the bag over to find the contents list. Even so, do take a look before buying -- even if the front of the bag states that the product is ‘environmentally friendly.’ In an unregulated industry, those words can mean just about anything,” she said.
In terms of environmental harm, calcium magnesium acetate can be an acceptable option.
“It’s a salt-free product made from limestone and acetic acid,” Smith said.
Calcium chloride ranks as being less damaging than some deicer products.
“Experts tend to rate sodium chloride – note the ‘sodium’ in its name – as the worst,” Smith said.
Humans’ oldest known way to make land incapable of growing plants is to “sow” salt.
In most cases, however, using a salt-based deicer as its bag recommends will just cause plant injury, she said. This sometimes can lead to plant death. Or, it can just include leaf or needle browning, leaf or needle loss, or witches’ broom development.
(Witches brooms are many densely clustered shoots or twigs, typically growing from a single point. They often resemble a Medieval broom, and are a symptom that something has gone wrong.)
Even if plants don’t exhibit signs of salt injury when they start actively growing again in spring, high salt levels in the soil will keep them under stress, Smith warned. This, in turn, will make the plants vulnerable to insect and disease problems
“Salt can actually damage concrete – especially new pads and walks. It increases the impacts of winter’s freeze and thaw cycles,” Smith said. “Unfortunately, salt spray along street easements can be unavoidable. In that case, all you can do is pray for your driveway and plant accordingly along the street.”
Plants that are more tolerant of salt include: gingko, Japanese tree lilac, birch, redcedar, red and white oak, fine fescue, and rugosa rose. Plants too sensitive for salted areas include basswood (linden), white pine, red maple, sugar maple, and Kentucky bluegrass.
“Increasing the soil’s organic matter content and watering by hand when the ground thaws can help leach salt out of the soil and away from plant roots. That can help limit unavoidable exposure and injury, too,” she said.
Contacts: Kathleen Ward, firstname.lastname@example.org
Jennifer Smith, (785) 843-7058 or email@example.com