Garden Myth Busters! Vinegar for Weeds

Based on an intern project by Rachel Vecchio, Certified Master Gardener

THE MYTH: Vinegar is an effective way to kill weeds.

THE REALITY: Household vinegar has long been heralded for its many uses around the home and garden, but is it actually an effective weed control method? 

Acetic acid, commonly referred to as vinegar, is available in different concentrations which affects its efficacy. Household vinegar has a five percent acetic acid concentration while herbicidal strength vinegar has an acetic acid concentration ranging from 10 percent to 20 percent in commercially available acetic acid sprays.

grass Vinegar is considered a contact herbicide, not a systemic one, which means it kills the foliage of any and every plant with which it comes into contact – weed or otherwise. Further, as a contact herbicide, it damages and kills the plant foliage/top growth. It doesn’t move down into and kill the root.

So, how effective is acetic acid for weed control? According to a 2001 study conducted by the Cornell Cooperative Extension of Rensselaer County, New York, the following weed control results were observed after one application of product:

24 hours 2 Weeks 5 Weeks 9 Weeks 13 Weeks
5% acetic acid 93.3% 74.7% 46.7% 33.3% 33.3%
20% acetic acid 98.3% 96.0% 92.7% 76.0% 66.0%
Glyphosate 53.3% 97.7% 99.3% 96.7% 95.0%
Source: http://ccerensselaer.org/resources/using-acetic-acid-vinegar-as-a-broad-spectrum-herbicide

From this study, it is clear that while both household vinegar and herbicidal strength vinegar are effective as initial and short-term weed control,  they are not effective for longer-term control. As a result, multiple applications of  vinegar are required to maintain anything close to the  weed control gained by use of a commercial synthetic herbicide, such as glyphosate . The additional applications required make vinegar a more expensive product to use per square foot and more time consuming to apply than synthetic herbicides.

Additionally, while the higher concentration acetic acid sprays are substantially more effective than household vinegar, many of these products come with a “Danger” symbol or word and can cause severe and permanent injury to skin and eyes, similar to synthetic herbicides. One could argue that if a person chooses to use an acetic acid spray, the injury risk is actually greater than with a synthetic herbicide because multiple applications are required to achieve the same weed control as from a synthetic product.

Conclusion: The use of vinegar as an herbicide does provide short-term weed control benefits, but ongoing and longer-term weed control is better accomplished with mechanical controls (pulling weeds) or barrier controls (mulch) first, and synthetic herbicide controls second.

SOURCES/REFERENCES:

Chinery, D. 2002. “Using Acetic Acid (Vinegar) As A Broad-Spectrum Herbicide.” Cornell Cooperative Extension of Rensselaer County. http://ccerensselaer.org/resources/using-acetic-acid-vinegar-as-a-broad-spectrum-herbicide

Gillman, J. 2011. “Vinegar: A Garden Miracle!” The Garden Professors. http://gardenprofessors.com/vinegar-a-garden-miracle

Mason, S. “Vinegar – Salad Dressing or Weed Killer?” University of Illinois Extension. http://web.extension.illinois.edu/cfiv/homeowners/070913.html

Smith, S.  2015. “Vinegar: Is it a “Safer” Herbicide?” Ohio State University Extension, Fairfield County. https://fairfield.osu.edu/news/vinegar-it-%E2%80%9Csafer%E2%80%9D-herbicide

Smith-Fiola, D. and S. Gill. 2017. “Vinegar: An Alternative to Glyphosate?” University of Maryland Extension. https://extension.umd.edu//sites/extension.umd.edu/files/_docs/programs/ipmnet/Vinegar-AnAlternativeToGlyphosate-UMD-Smith-Fiola-and-Gill.pdf

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