B. Rosie Lerner
Purdue Extension


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Conquer Weeds with Vinegar?

If fighting weeds in your garden has you in a pickle, you'll be interested in a USDA research report about using acetic acid (vinegar) as an herbicide.  

USDA researchers confirmed that acetic acid is effective at killing some common weed species, including Canada thistle, lamb's-quarters, giant foxtail, velvetleaf and smooth pigweed.

Weeds were hand-sprayed with various solutions of vinegar, uniformly coating the leaves. The researchers found that 5- and 10-percent concentrations killed the weeds during the first two weeks after emergence from the soil. Older plants required higher concentrations of vinegar to kill them. At the higher concentrations, vinegar had an 85- to 100-percent kill rate at all growth stages. However, perennial weeds, such as Canada thistle, were only temporarily knocked back; the roots survived to sprout new shoots.

Even though vinegar is an acid, it breaks down quickly in the soil and, therefore, is not likely to accumulate enough to affect soil pH for more than a few days.

Corn is the only crop thus far that USDA scientists have reported on the use of vinegar to control weeds without harm to the crop. Vinegar causes a rapid burn to plant tissue of susceptible species, so unintended injury is quite likely without knowing more information. Further studies are needed to know whether other crop plants and ornamentals can tolerate the vinegar.

Ordinary household vinegar is about a 5-percent concentration. Stronger solutions that are labeled for use as herbicides are now available from some retailers, including http://www.sumrset.com/new_herbibide.htm, http://www.greensense.net/, http://www.bradfieldorganics.com/ and http://www.biconet.com/lawn/burnout.html.

Note that vinegar with acetic acid concentrations greater than 5 percent may be hazardous and should be handled with appropriate precautions. Vinegar solutions of 11-percent strength can cause skin burns and eye injury. Also note that the use of a vinegar product for killing weeds, unless the material is specifically labeled as a herbicide, is illegal and a violation of federal pesticide laws. Always read and follow all pesticide label directions.

More information about the USDA study is available online at http://www.ars.usda.gov/is/pr/2002/020515.htm.


Writer: B. Rosie Lerner
Editor: Olivia Maddox