Laundry detergent can kill grass, often turning the lawn into a scorched, brown patch. The damage results from concentrated chemical ingredients, though severity depends on the detergent type and volume of the spill. While highly diluted detergent may cause no harm, a concentrated spill can quickly prove toxic to turfgrass. Understanding the chemical reactions in the soil and on the grass blades explains why this common household item is detrimental to plant life.
The Chemical Mechanisms That Harm Grass
The primary cause of grass death is a dual assault involving high salt content and surfactants. Detergents contain sodium salts, which, in high concentrations, create osmotic stress. This process draws water out of the grass roots and cells to balance the salt concentration, effectively dehydrating the grass from the inside out and causing what looks like a chemical burn.
Surfactants, the compounds that lift grease and dirt, damage the plant structure by breaking down the protective waxy cuticle covering the grass blades. This cuticle is the plant’s natural defense against water loss and environmental stress. Once compromised, the grass is left vulnerable, leading to rapid desiccation and an inability to regulate its internal water balance.
Many detergents, particularly powdered varieties, are highly alkaline, sometimes ranging from pH 10 to 11.5. This elevated alkalinity disrupts the healthy chemistry of the soil, making it difficult for grass roots to absorb necessary nutrients. The combination of salt toxicity, cuticle breakdown, and altered soil pH creates a hostile environment that quickly overwhelms the plant’s ability to survive.
Factors That Determine the Severity of Damage
The outcome of a spill is influenced by the concentration and volume of the detergent reaching the grass and soil. A large, concentrated spill creates severe, localized toxicity due to the volume of sodium salts and surfactants. Conversely, the highly diluted flow from a washing machine’s gray water drain may not cause immediate harm, but repeated exposure can lead to a slow buildup of harmful compounds in the soil.
The physical form of the detergent plays a role, as powdered detergents often contain a higher concentration of inorganic sodium salts and alkaline builders than their liquid counterparts. These ingredients contribute to a more drastic increase in soil salinity and pH, which can persist in the soil for a longer period.
Soil composition also determines the duration of the toxicity. Highly absorbent clay soils tend to hold onto the chemical residue longer than porous, sandy soils, which allow for quicker leaching and dispersion. Furthermore, specific ingredients like boron, found in some washing powders, can greatly increase the toxicity because boron is poisonous to plant life. The depth of the detergent’s penetration into the soil dictates how much of the root system is affected and the effort required for remediation.
Immediate Steps for Lawn Recovery
The most important step following a detergent spill is immediate and massive dilution with water to flush the chemicals out of the grass and soil. Soak the affected area to dilute the concentration of salts and surfactants, applying at least one gallon of water for every half-cup of detergent estimated spilled. Repeat this heavy watering several times over the next 24 to 48 hours to encourage the toxic compounds to leach below the root zone.
If the detergent was a powder or high-alkaline formula, the soil’s pH may be elevated, requiring a soil amendment to restore balance. Applying gypsum (calcium sulfate) can help flush excess sodium from the soil, while elemental sulfur can gradually lower the soil’s pH back toward a neutral range. Work these amendments lightly into the top layer of the soil and water them in after the initial dilution phase is complete.
If the grass blades have already turned fully brown and dry, they are likely dead, and no amount of watering will bring them back. At this point, remove the severely damaged grass and the top inch or two of contaminated soil. Introduce fresh, uncontaminated topsoil, and then proceed with reseeding or laying new sod to successfully repair the lawn patch.