But as with many home-brewed garden remedies and even packaged organic ones, we need to ask whether science supports the theory—and if it’s safer. Hint: There’s no scent of salad dressing in my garden (and no chemicals, either).
Related: What The Weeds In Your Yard Can Tell You About Your Soil Quality
Vinegar’s active ingredient, acetic acid, can be produced naturally through bacterial fermentation, as in apple-cider vinegar, or industrially, via chemical reactions from such source materials as methanol. But concentrations strong enough to be effective against anything but the youngest, most tender weeds, vinegar is no longer a food product but an herbicide called horticultural vinegar, and not so friendly.
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The Dangers of using vinegar in your garden
In concentrations this strong, vinegar becomes hazardous and can cause environmental damage. Vinegar is a contact or “burndown” herbicide, killing what it touches within hours or days. The worst part is, it looks like it’s working, but then weeds resprout from the roots, particularly perennial species.
That partial success worries Jeff Gillman, author of The Truth about Organic Gardening, because it often incites a gardener to continue using vinegar, even if it's not the best for his or her garden. The gardener—seeing results but not entirely satisfied—often trades up to higher concentrations, replacing household vinegar (5 percent acetic acid) with a horticultural product (typically 20 percent).
Related: 5 Ways Weeds Are Actually Good For Your Lawn
Despite the signal word danger on most such labels, gardeners may instead just see vinegar and be careless. Sobering details: In concentrations over 11 percent, acetic acid can burn skin and cause eye damage, and concentrations of 20 percent and above are corrosive to tin, aluminum, iron, and concrete and can even cause blindness. Such herbicides are meant to be applied while wearing goggles and protective clothing.
And then, Gillman says, there is potential environmental damage—such as to the toad or salamander shading itself beneath those weeds. “If you’re talking about just-sprouted seedlings, and you go after them right away with household vinegar, fine,” says Gillman. Otherwise, it’s better to reach for a hand cultivator than a spray bottle.
How to manage weeds without vinegar
Wary of horticultural vinegar? Rightly so.
Instead, preventive mulches, well-timed cultivation, and Jeff Gillman’s and my favorite remedy—hand-weeding—are indisputably effective, and 100 percent environmentally safe.
Additionally, here are more helpful organic weed control methods to help you skip the vinegar, and here are some more specific tips to help you get rid of crabgrass without harmful chemicals.
Margaret Roach runs the popular AWayToGarden.com website and podcast.