Sodium bicarbonate, commonly known as baking soda (NaHCO₃), is a household compound often viewed as a natural and inexpensive alternative for various lawn care issues. While non-toxic to humans, baking soda is capable of causing significant damage to turfgrass if applied incorrectly or in high concentrations. The answer to whether baking soda hurts grass is definitively yes, as its chemical properties can create an environment hostile to healthy plant life.
Common Applications on Lawns
Many homeowners turn to sodium bicarbonate as a quick remedy for common turf ailments. It is frequently employed as a fungicide because its alkaline nature inhibits the growth and spread of certain fungal pathogens, such as powdery mildew. The goal is to alter the conditions the fungus needs to thrive without harming the underlying grass. Baking soda is also used as a non-selective spot treatment to kill small, undesirable weeds like crabgrass, acting as an herbicide by dehydrating the foliage it contacts.
How Sodium Bicarbonate Damages Grass
Damage to turfgrass from sodium bicarbonate occurs through two primary mechanisms: salt-induced osmotic stress and alkalinity disruption. The compound is a salt, containing sodium ions (Na⁺) that accumulate within the soil and on the plant tissue. When the concentration of sodium becomes too high, it draws water out of the grass cells. This process, known as osmotic stress, leads to cellular dehydration, causing the grass blades to dry out and display symptoms of “burn.” The visible yellowing or browning is the result of the plant tissue being unable to retain the moisture necessary for survival.
The second factor is the compound’s highly alkaline nature; a 1% aqueous solution of sodium bicarbonate has a pH of approximately 8.5. Turfgrass generally thrives in a slightly acidic to neutral soil pH range, typically between 6.0 and 7.0. Applying an alkaline substance directly to the grass or soil surface causes a rapid, localized spike in pH. This sudden change disrupts the grass’s ability to efficiently absorb essential nutrients from the soil, leading to chlorosis and stunted growth.
Guidelines for Safe Application
To minimize damage, sodium bicarbonate should only be used as a targeted spot treatment, never as a broadcast application. For a fungicidal spray, mix one to two tablespoons of baking soda with a gallon of water, often adding liquid soap to help the solution adhere to the leaves. Test this diluted solution on a small patch of grass first and wait several days to observe any adverse reactions. Apply the solution when the grass blades are dry, directing it only onto the affected area and avoiding overspray.
If an accidental heavy application occurs, or if signs of minor yellowing appear after treatment, immediately and thoroughly flush the area with plain water. This action helps dilute the concentration of sodium ions and restore the soil’s balance, mitigating potential long-term damage.