The problem with vinegar
By Wendy Hanson Mazet
As gardeners, we tend to get creative on how we deal with weeds in our yard. When it comes to what we choose to use, it all depends on our preferences, may it be mulching, hand pulling, getting a goat or purchasing a product. The newest fad to hit the internet is using common household vinegar to kill weeds.
As Master Gardeners, we are trained to never use, nor suggest using, a product for any other purpose but the one printed on its label. Look at a label of distilled white vinegar, the typical household vinegar, and you will see recipes for food or for cleaning, not for weeds. Labels may include recipes for meats, pasta salad with sweet vinaigrette, cleaning the coffee maker, removing grease and cleaning windows.
So, what is it about vinegar that makes people want to kill weeds with it? Household vinegar consists of approximately 5 percent acetic acid and 95 percent water, unless you purchase cleaning vinegar which is 6 percent acetic acid.
According to Washington State University, acetic acid is one of the few chemicals that has two common names, which are defined by concentrations. Vinegar means concentrations up to 8 percent. Acetic acid means concentrations higher than 8 percent. When the concentration is low enough to be called vinegar, it is a food product. When the concentration is high enough to be called acetic acid, and it is used to kill weeds, it is a pesticide.
Acetic acid as a true nonselective plant killer is commonly available as a 20 to 30 percent acetic acid concentration, and the acid is considered effective on young, actively growing broadleaf weeds. The household version of 5 percent is not generally strong enough to damage and dry out the weed’s leaves, unless something else is added. Why is making your own vinegar solution a bad idea? First, studies have shown acetic acid in concentrations above 5 percent can cause severe burns to skin and eyes. Homemade concoctions do not carry any warning labels on how or when to use them or what to do if there is an accident.
Herbicidal vinegar with 20 to 30 percent acetic acid is labeled and available for use in killing young weeds. Always read the label carefully; it is a legal requirement that you read the label, understand it and use the product according to its label.
On the label, you’ll find the signal word. For herbicidal vinegar, it is generally DANGER. Acetic acid is highly corrosive and can cause irreversible eye damage. Goggles or face shields are needed when handling this product. The USDA issued this warning in their research report: “WARNING: Note that vinegar with acetic acid concentrations greater than 5 percent may be hazardous and should be handled with appropriate precautions.”
So what is right for you? Cooperative Extension staff and volunteers do not recommend homemade concoctions as we follow the label, as required by law. Before you consider using anything that is not labeled as a weed killer, research everything that has been tested and studied so you can make the best, educated decision for yourself. There are numerous options available that are labeled as natural weed suppressors or killers, including organic and synthetic options.
Smith-Fiola, D., & Gill, S. (2014). Vinegar: An Alternative to Glyphosate? Retrieved July 5, 2017, from https://extension.umd.edu/sites/extension.umd.edu/files/_docs/programs/ipmnet/Vinegar-AnAlternativeToGlyphosate-UMD-Smith-Fiola-and-Gill.pdf.
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