Why It Can Be Dangerous To Use Vinegar To Kill Weeds

Vinegar may sound like a good alternative to chemicals, but you should think twice before using it.

May 18, 2017
spray with vinegar
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The idea sounds well-intentioned: Stop using chemical weed killer, and spray vinegar instead.

(Whether you're starting your first garden or switching to organic, Rodale’s Basic Organic Gardening has all the answers and advice you need—get your copy today!)

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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.

Related: The Politics Of Invasive Species

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

hand weeding
Nicola Tree/getty

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.

Tags: weedsVinegar