Vinegar, an aqueous solution of acetic acid, is a common household substance. Many people propose it as an effective, non-toxic remedy for controlling unwanted plant growth. When applied to foliage, the acidic nature of this solution can indeed cause rapid and visible damage to both weeds and desirable plants, including grass. Assessing its effectiveness requires understanding how acetic acid interacts with plant tissue.
How Acetic Acid Damages Plant Tissue
Acetic acid functions as a non-selective, contact herbicide, meaning it only affects the plant parts it directly touches and does not travel systemically. When the solution is sprayed onto leaves and stems, it quickly begins to break down the plant’s protective outer layers. The acid targets and disrupts the integrity of the plant’s cell membranes in the foliage. This rapid dissolution of the cell walls causes the cell contents to leak out, leading to immediate desiccation of the exposed plant tissue. The result is a quick “burn-down” effect, often visible within hours, especially on warm, sunny days.
The Critical Difference in Vinegar Strength
The effectiveness of vinegar is directly tied to its concentration of acetic acid. Common household white vinegar, sold for culinary and cleaning purposes, contains only about 5% acetic acid by volume. This low concentration may show some efficacy against very small, newly germinated seedlings, but it is often insufficient for reliable control over larger, established plants. For reliable herbicidal action, specialized horticultural vinegar products are necessary, typically ranging from 10% to 30% acetic acid. The increased concentration significantly enhances the acid’s ability to penetrate the plant’s waxy cuticle and destroy the underlying cells.
Practical Limitations on Plants and Grass
Vinegar’s non-selective nature means it will damage any green plant material it contacts, making it unsuitable for spot-treating weeds within a lawn. Applying it to broadleaf weeds will also severely damage or kill the surrounding grass. The primary limitation of acetic acid is its inability to affect the plant’s root system, since it is a contact-only herbicide. While the top growth may appear dead, the root structure often remains intact and viable beneath the soil, especially for perennial weeds like dandelions or thistles. These plants frequently regrow new foliage, requiring repeated treatments; vinegar works best only on very young annual weeds with shallow root systems.
Soil Acidity and Application Safety
When acetic acid contacts the soil, it temporarily lowers the soil’s pH level, making it more acidic. This effect is usually short-lived, as the acid quickly breaks down through natural chemical reactions and microbial activity. Unless applied repeatedly in heavy quantities, vinegar generally does not cause long-term soil acidification. While household vinegar is safe, the higher concentrations found in horticultural products are corrosive and require careful handling. Solutions above 11% can cause chemical burns and serious eye injury, requiring users to wear protective gear, such as gloves and eye protection.