We often hear of home remedies that have not been scientifically tested. Vinegar has been suggested as an effective herbicide, but until recently it had not been studied for effectiveness. The USDA’s Agricultural Research Service has finally put vinegar to the test. They used concentrations of varying strengths including 5, 10 and 20 percent.
Household vinegar is close to a 5 percent solution. Weeds tested included lambs-quarters, giant foxtail, velvetleaf, smooth pigweed and Canada thistle.
Weeds were hand-sprayed so that the leaves were uniformly coated with material. Young plants within the first two weeks of life were killed with the 5 and 10 percent solution. Higher concentrations provided 85 to 100 percent kill regardless of the size of the weed.
Canada thistle proved to be exceptionally susceptible to vinegar. The 5 percent solution gave 100 percent kill of top growth. Vinegar sold as a herbicide is most often a 20% solution.
Note that all weeds tested were annuals except the thistle. Vinegar is not translocated, so it would burn the top growth of perennials but would be unlikely to kill established plants. Vinegar is commonly made from wine, cider or malt, though a wide variety of materials can be used. This study included only vinegar made from fruits or grains, so it conforms to organic farming standards. (Ward Upham)
