Crabgrass is an annual weed that aggressively invades and overtakes lawns. This common nuisance thrives in hot, dry conditions, spreading rapidly because a single plant can produce thousands of seeds throughout the summer season. While many commercial herbicides exist, some homeowners prefer a readily available, non-toxic, and inexpensive method for control. Baking soda, known chemically as sodium bicarbonate, offers a simple, household alternative for targeting this persistent weed.
The Science Behind Baking Soda’s Effectiveness
Sodium bicarbonate acts as a potent, non-selective herbicide due to its chemical composition and its effect on plant cells. When applied directly to the foliage, the compound rapidly increases the alkalinity (pH level) on the surface of the plant tissue. This sudden, extreme change in pH creates a hostile environment that disrupts the weed’s normal cellular functions.
A more immediate and destructive mechanism is baking soda’s function as a strong desiccant. The high sodium content acts like a salt, actively drawing moisture out of the crabgrass cells through osmosis. This cellular dehydration causes the leaves to quickly wilt, brown, and shrivel, effectively burning the weed from the outside in.
Detailed Application Guide for Killing Crabgrass
Effective treatment depends on precise, targeted application, and there are two primary methods for utilizing baking soda.
Dry Application Method
This method is best suited for small, isolated clumps of crabgrass. To prepare, lightly mist the crabgrass patch with water so the leaves are damp, allowing the fine powder to stick securely to the foliage. Sprinkle a small amount of baking soda directly onto the center of the clump, ensuring minimal contact with the surrounding desirable turf.
Liquid Spray Method
The liquid spray is more suitable for areas with widespread, but manageable, crabgrass growth. An effective ratio is mixing two to three tablespoons of baking soda into one quart of water. For improved adherence to the weed’s waxy leaves, a few drops of liquid dish soap can be added as a surfactant. Pour this solution into a handheld spray bottle for accurate spot-treating.
Timing the Application
For both methods, timing is an important factor for success. Apply the treatment when the crabgrass is actively growing, ideally on a calm, sunny day with no rain forecasted for at least 24 hours. The direct sunlight and lack of moisture allow the desiccant properties of the sodium bicarbonate to work most efficiently. The crabgrass should turn dark brown or black within a few hours or by the next day, indicating the treatment was successful.
Preventing Damage to Desirable Turf and Plants
It is important to remember that sodium bicarbonate is a non-selective compound, meaning it will cause damage to any plant tissue it touches, including your lawn. Over-application or imprecise targeting can lead to brown spots in desirable turfgrasses like fescue or bluegrass. For this reason, always use the baking soda as a direct spot-treatment, avoiding broadcast application over a wide area.
The high sodium content in baking soda also poses a risk of soil salinity buildup, which can harm the long-term health and fertility of the soil if frequently or heavily used. Avoid treating lawns that are already stressed from drought, heat, or disease, or those that have been newly seeded. If you notice signs of distress in the surrounding grass after treatment, the soil may need to be flushed.
To mitigate sodium buildup, gently and thoroughly water the treated area a day or two after the crabgrass has died and been removed. This process, known as leaching, helps to dissolve and wash the excess sodium ions deeper into the soil profile, moving them away from the roots of the desirable turf. Monitoring the treated area and using the least amount of product necessary will help maintain a healthy balance.