Salt has long been touted as a safe, organic weed killer. While salt is effective at controlling weeds, however, it may cause soil problems and damage other plants.
Salt is most effective when mixed with water at a rate of 1 pound salt per gallon of water and sprayed directly on leaves. It can also be applied dry directly to the base of the plant. Salt works as a weed killer by depriving the plant of moisture.
The residue remains in the soil for weeks after use, and nothing will be able to grow there until the salt has dissipated.
Salt can also leach into the earth and affect plants several feet away from the original application.
When treating an area like a driveway, where you will not be planting anything, salt can be a good alternative to harsh chemical treatments. Make sure to use only a small amount to ensure that nearby plants are not affected.
Other organic methods of weed control are just as effective as salt without the problems. Corn gluten meal, for example, can be used to dehydrate weed seeds and prevent them from sprouting, or boiling water can be applied directly to weeds to kill them.