Most deicing salt is plain old table salt: sodium chloride. Both sodium and chloride are damaging to plants. In addition, sodium is also damaging to soil structure, ruining drainage.
Salt splashed onto the twigs and buds of deciduous plants kills them, resulting in a dense growth of side branches called a witch’s broom. Evergreens foliage turns brown from salt deposits.
Salt in the soil has a more insidious effect and is difficult to diagnose. Damage usually appears in spring or early summer, after the plants leaf out. Plants are stunted, leaves may be scorched, and growing tips die back.
In addition, sodium damages the soil structure, impeding drainage.
Although sodium chloride is the least expensive and most common deicing salt, several other chemicals are available.
Calcium chloride is less injurious to plants then sodium chloride, but more corrosive to concrete.
Potassium chloride is even more damaging to plants than sodium chloride.
Urea is a nitrogen source. It won’t burn plants, but might cause excess fertilization.
Calcium magnesium acetate (CMA) is non-corrosive and not damaging to plants. However, it is very expensive.
Using Deicing Salts
Try to use as little salt as possible around your home. Here are some tips to reduce the amount of salt you use:
- Clear snow first. Don’t use salt to melt the snow, but to get rid of the residue to make secure footing.
- Use deicing salts to undercut thick ice, not melt it; the pellets will melt through to the ground and melt the ice there, making the ice easier to remove with a shovel.
- Use sand or (clean) kitty litter instead of salt. It doesn’t melt ice, but gives traction. Or mix sand and salt to do a little of each.
- Select deicing salts with a low burn potential, such as urea or CMA.
Avoiding Splash Damage
You can’t do much about the salts used to clear the street you live on, but you can protect plants somewhat.
Make burlap or plastic shields or wraps to keep salty slush from splashing onto streetside plantings.
As soon as the ground thaws in the spring, irrigate heavily to leach the salt below the root zone of the plants. If your city uses sodium chloride, spread gypsum first, at a rate of 200 pounds per thousand square feet, then irrigate heavily. The calcium in the gypsum (calcium sulfate) will displace the sodium, allowing it to be leached out.
Select salt-tolerant plants for streetside plantings.
|Perennial ryegrass||Tall fescue|
|Alpine currant||Pfitzer Juniper|
|Japanese tree lilac||Staghorn Sumac|
|Mock orange (Philadelphus)||Winged Euonymus|
|Black locust||Norway maple|
|Colorado spruce||Silver maple|
|Eastern red cedar||Tree-of-heaven|