Bermuda grass is a highly aggressive, warm-season perennial grass that is difficult to eradicate due to its extensive network of underground stems (rhizomes) and above-ground runners (stolons). While often sought after for turf, it becomes an invasive weed when it encroaches on garden beds. Many people search for non-toxic control options, such as vinegar, which is a solution of water and acetic acid.
The Mechanism: How Acetic Acid Kills Plants
Acetic acid functions as a non-selective, contact herbicide, meaning it causes damage only to the plant tissue it directly touches. The mechanism is rooted in the acid’s low pH, which rapidly breaks down the cell walls of the plant tissue. This causes the cells to lose their internal fluids quickly, resulting in desiccation, or extreme drying out, which causes the visible “burn” on the foliage. This action is fast, often resulting in the browning and wilting of the treated plant parts within hours of application. Since the acid breaks down quickly in the environment, it has little residual effect on the soil.
Efficacy Against Bermuda Grass Roots
While vinegar is highly effective at causing a rapid “top-kill” of the Bermuda grass foliage, its effectiveness against the roots is significantly limited. Acetic acid does not travel systemically through the plant to reach the subterranean network of rhizomes and stolons. Bermuda grass is a perennial weed, meaning it possesses substantial energy reserves stored within its deep root system. Even when the leaves are burned away, the extensive rhizomes remain intact beneath the soil surface, allowing the plant to quickly regrow new shoots. Repeated applications are necessary to continually burn down the foliage, which slowly depletes the rhizomes of their stored energy.
Household vs. Horticultural Vinegar: Application and Safety
The concentration of acetic acid is the primary factor differentiating household vinegar from horticultural products, dictating both efficacy and safety. Standard household vinegar contains approximately 5% acetic acid. This low concentration is generally insufficient to effectively burn down mature Bermuda grass, though it may work on very young seedlings. Horticultural vinegar, sold specifically as a weed killer, contains significantly higher concentrations, ranging from 10% to 20% or more. These higher-strength solutions are far more effective at achieving the necessary top-kill on established Bermuda grass. For best results, the product should be applied on a hot, sunny day, which enhances the desiccation effect.
Safety Precautions
Handling horticultural vinegar requires caution due to the corrosive nature of the concentrated acid. At 10% concentration and above, acetic acid can cause chemical burns to the skin and eyes. Users must wear appropriate personal protective equipment, including rubber gloves, long sleeves, and eye protection. Furthermore, concentrated vinegar is non-selective and will damage any desirable plants it touches, requiring precise application.