Rock salt is commonly used as a deicing agent, helping prevent winter accidents on roads, driveways and sidewalks. Road crews often add rock salt as a preventative measure when wintry weather is predicted. The same qualities that help the salt break through the ice make it deadly for your lawn. In addition to harming your existing lawn, rock salt can keep grass from growing for years.
Salt removes the moisture from the soil, keeping it from getting to your lawn’s roots. The plants become dehydrated and die. If the salt touches a growing grass blade, it takes the moisture out of the blade as well, leaving it brown and withered. Touching dormant grass blades doesn’t do much damage, but the damage to the soil can keep dormant grass from getting the water it needs to grow in warmer weather.
Salt tends to separate into its basic ions when dissolved in water. The sodium ions block grass roots from getting necessary nutrients such as calcium, potassium and magnesium. The chloride ions are absorbed by the roots instead, growing to toxic levels. When the grass contains too much chloride, it can’t produce chlorophyll effectively and will starve when it can’t turn the sun’s light into energy.
Soil naturally contains small levels of salt, especially if it’s fertilized regularly. A few wayward chunks of rock salt won’t harm your lawn. Large amounts can stay in the soil for years, though, accumulating every year until the salt creates an environment toxic to your grass. Salt stays there until it’s leached away by rainwater, which means you won’t be able to plant new grass until the salt is gone. You can speed this process by watering the damaged area thoroughly. Give it deep soakings daily as soon as the weather is warm enough to help drain the salt below the lawn’s root level.
You can’t control what your local government uses to keep roads ice-free on those occasions when icy conditions are expected, but you can help protect the areas of your lawn near the road by installing temporary snow or silt fencing. It blocks much of the salt, keeping it off your lawn. You can also cover your grass with plastic sheeting, held down with rocks or landscape staples. For your driveway or sidewalks, try an alternative ice-melt product. Garden centers often carry some that are labeled as safe for landscape use, or you can try sand or kitty litter to give you traction over small, slippery areas.