Chlorine, a chemical element widely used in household products and swimming pools, can severely damage or kill grass depending on its concentration and the duration of exposure. This common disinfectant poses a significant risk to turfgrass health. While small splashes of diluted pool water are generally tolerated, large volumes or high concentrations, such as from pool drainage or spills of cleaning products, can quickly lead to plant death. Understanding how this chemical interacts with turfgrass is the first step in protecting your lawn.
The Chemical Harm Caused by Chlorine
Chlorine causes damage to turfgrass at a cellular level because it acts as a strong oxidizing agent. When chlorine contacts plant tissue, it quickly breaks down and destroys the organic molecules that make up the grass blades and roots. This oxidizing action denatures the proteins and lipids within the plant cells, leading to a chemical burn that destroys the grass’s structure and function. It also rapidly destroys chlorophyll, the pigment responsible for photosynthesis, which is why the grass quickly loses its green color.
Beyond its direct toxic effects, chlorine exposure can also disrupt the soil environment necessary for healthy grass growth. High concentrations of chlorinated water significantly alter the soil’s pH balance, moving it outside the ideal range of 6.0 to 7.0 that turfgrass prefers. This sudden shift hinders the grass’s ability to absorb essential nutrients, effectively starving the plant. Furthermore, many chlorine sources introduce salts into the soil, which leads to osmotic stress. This increased salinity draws water out of the grass roots, causing dehydration and impeding the plant’s ability to take up water and nutrients, a phenomenon known as “salt burn.”
Recognizing Chlorine Damage on Grass
Identifying chlorine damage requires looking for a distinct pattern and speed of discoloration that differentiates it from other common lawn problems like drought or disease. The most characteristic symptom is the rapid bleaching, yellowing, or browning of the grass blades, often occurring within hours or a few days of exposure. This discoloration is typically concentrated in the areas where the chlorinated water made contact, resulting in distinct, localized patches.
For instance, a spill might result in a circular dead spot, while pool splash-out often creates marginal leaf burn along the edges of the turf nearest the water source. Unlike the gradual, uniform yellowing seen with nutrient deficiencies or the patchy, irregular browning of fungal diseases, chlorine damage presents as an immediate, intense burn mark. The rapid necrosis, or tissue death, is a direct result of the chemical’s oxidizing power, causing the affected areas to appear brittle and dry. This quick onset helps confirm that the damage is chemical, not biological or environmental, in origin.
Immediate Steps for Recovery and Prevention
Immediate Recovery
The most important and immediate action upon noticing chlorine exposure is to flush the affected area thoroughly with clean, fresh water. Deeply watering the spot dilutes the concentration of chlorine and any residual salts in the soil, effectively washing the harmful chemicals away from the grass roots. This process of repeated irrigation helps to minimize the chemical burn and works to restore the soil’s natural chemical balance. It may be necessary to repeat this deep watering over several days or weeks to fully leach the contaminants from the root zone.
If the grass dies completely, which often happens with highly concentrated spills like undiluted bleach, reseeding or patching with sod will be necessary to restore the lawn. Before attempting to reseed, remove the dead grass and lightly loosen the contaminated topsoil to prepare a fresh seedbed.
Long-Term Prevention
For long-term prevention, manage all sources of chlorinated water, particularly from swimming pools. When draining a pool for maintenance, the water should be diverted away from the lawn and into a proper drainage system.
To reduce the risk of damage, allow the chlorine concentration in the pool to drop to very low levels, ideally below 0.1 parts per million, before draining onto the lawn. This is achieved by ceasing chlorine additions and allowing sunlight to naturally dissipate the chemical for about ten days prior to draining. When household cleaning products containing chlorine are used outdoors, ensure they are heavily diluted and used away from turfgrass areas to prevent accidental chemical burns.