Information About Using Vinegar As a Weed Killer

Household vinegar is not very effective as a weed killer, but acetic acid, the active ingredient in vinegar, is effective in high concentrations.

Increasing environmental consciousness has prompted a search for weed killers that are safe for humans and the environment. Organic gardeners are always on the lookout for an environment- and human-safe herbicide. Many people turn to the pantry for alternatives to traditional herbicides, using vinegar, salt, bleach, dish soap and disinfectants to attempt to kill weeds. Using products for purposes other than the ones they are designed and labeled for can be ineffective at best, but may even be dangerous. Household vinegar is used for many purposes, from salad dressing to window cleaning. Its use as a weed killer, though, has been deemed mostly ineffective by research.

Acetic Acid

Household vinegar is usually 5 percent acetic acid and 95 percent water. All living organisms contain acetic acid. It is readily broken down into carbon dioxide and water. In the concentration found in household vinegar, acetic acid has little impact on weeds. Studies show that it kills about 5 percent of the weeds it comes into contact with in that concentration.

Vinegar Application

Vinegar can be effective against some weeds in certain applications. The vinegar is usually applied with a spray bottle and must come into direct contact with the entire surface of the target weed. The acidity of the vinegar dries out the leaves, damaging the leaf surface. The vinegar does not affect the root of the weed, so the vinegar treatment is mostly ineffective against perennial weeds. Vinegar can also damage surrounding, desirable plants, so the effective use of vinegar as an herbicide is limited mostly to applications such as weeds in sidewalk and driveway cracks.

Dangers of Acetic Acid

While household vinegar is safe to consume, when acetic acid is found in concentrations high enough to be effective against weeds, it is very dangerous. Acetic acid in concentrations over 11 percent can cause severe corneal damage to eyes upon contact, and chemical burns to skin. If you use these acetic acid products you should use eye and skin protection. Any herbicide that uses acetic acid as an active ingredient in a concentration sufficient to kill weeds should be clearly labeled regarding use and dangers, and be approved by the Environmental Protection Agency (EPA).

Commercial-Grade Vinegar

Commercial-grade vinegar is available with acetic acid in higher concentrations than household vinegar. While research shows that this vinegar should be more effective against weeds, it should not be used as an herbicide because it is not EPA-approved or labeled for use as an herbicide.

Acetic Acid Herbicides

Some herbicides are now on the market which use acetic acid as the active ingredient in 6- to 7-percent concentration. Studies have shown they are little more effective than household vinegar. The most effective use of acetic acid is in concentrations greater than 10 percent. Some herbicides now available contain acetic acid in 20-percent concentration. These herbicides are still effective only on the foliage of weeds.They should be labeled according to EPA regulations, and should note the danger associated with their use.

References

• University of Illinois Extension: "Vinegar- Salad Dressing or Weed Killer?" Sandra Mason
• Oregon Department of Agriculture: Fact Sheet for Vinegar/Acetic Acid Recommendations