Why Can Salt Be Used as a Weed Killer?
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How Salt Kills Weeds
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Salt is a desiccant. It absorbs nearby available moisture. Salt deposited on a plant results "exosmosis" and causes the water in the leaf to move out of the leaf. The areas of the leaf which are affected will look brown and burnt. Salt in the soil will dry out plant roots and damage the plant's ability to soak up moisture and nutrients. While this can damage landscaping in areas affected by sea spray or by road-salt run off, it can be used in selectively killing weed species by placing a strong salt solution directly on the weed targeted for elimination.
Using Salt as a Weed Killer
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Compared to many chemical weed killers, salt is relatively benign. Salt will leach through the soil, spreading to cause negative effects on surrounding plants as well as the targeted weed. Salt's use as a weed killer is not subject to legal regulations like chemical weed killers are, mainly because it does not present a major public health hazard. By the time salt reaches the water table or public water supplies, it is so diluted and is of minimal to no effect on drinking water safety, unlike some chemical weed killers. Using salt as a weed killer does have hazards, however. Call your local poison control center if a child or pet ingests the salt you have distributed to kill weeds,.
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Making a Salt-Based Weed Killer at Home
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Recipes for homemade salt weed killers vary widely in their recommendations as to salt concentration as well as the addition of other ingredients. Soap lowers the surface tension of water and makes the solution more easily absorbed into plants' cells and thus more effective. Vinegar increases acidity, which also adds to the effectiveness of a salt weed killer. Since salt in the soil will kill surrounding plants and may potentially render that area of soil unfit for growing for some period of time, it is best to use as low a concentration of salt as will work or to restrict the use of salt weed killers to areas such as cracks in a cement sidewalk, where no growth at all is desired. Plants vary in their sensitivity to salt, so experiment with different salt concentrations and the addition of soap or vinegar until you reach a solution effective for your yard care needs. You can also heat or even boil the salt water and pour it onto the weeds while hot, which is even more effective particularly on walks and patios. Be careful to avoid splashing the boiling water on yourself or others when using this method.
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- Photo Credit Cindy Hill
