Vinegar is an acetic acid solution produced by distilling fruits or grains. The solution has been used as an herbicide for many years and is considered organic for use by certified organic farmers. Acetic acid is biodegradable as it degrades in water and does not bioaccumulate in the soil. The results from using vinegar are not predictable, as weed varieties respond differently based on their structures.
Household vinegar contains a concentration of 5 percent acetic acid. Research completed by the United States Department of Agriculture has shown that household vinegar is strong enough to kill weeds during the first two weeks of growth. It was found that household vinegar worked best on the perennial Canada thistle, killing 100 percent of the top growth.
High Concentration Vinegar
A high concentration of vinegar is produced through additional distillation of the solution. A 20 percent solution is preferred for weed control, as USDA testing showed that this concentration killed the most weeds without affecting plant growth. Concentrations of vinegar that are higher than the 5 percent household vinegar showed an 85-100 percent weed kill rate at all growth stages, according to the USDA.
How to Use
Vinegar is applied to field crops as a spot treatment and as a blanket spraying program. The USDA is continuing to research how vinegar affects the crop plants during an overall spray application, resulting in spot spraying being the recommended method for application. Spot-treating crops with a 20 percent vinegar solution has an approximate cost of $20 per acre.
How it Works
Vinegar sprayed on a plant is absorbed by the leaves to kill off the green plant. Since vinegar is acetic, most plants cannot tolerate the increase in acid. Low concentrations of vinegar do not travel to the root system, which is why mature weeds are not killed off completely with this solution. Vinegar that has an acetic concentration higher than that of household vinegar is considered an herbicide and is labeled as hazardous. It is possible for the vinegar to burn skin or eyes, so caution must be taken during application.
A study completed by garden-counselor-lawn-care.com showed that an old-time recipe of one gallon of household vinegar and one ounce of dishwashing soap was effective at killing weeds in some situations. Weeds that have a waxy or fuzzy appearance did not respond to the treatment. Not all root systems were killed after application of the solution. Vinegar applied to the soil will kill roots; however, the effects on surrounding plants are not certain.