Is Your DIY Weed Killer Safe?
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You’ve seen it on Plant Tok, where gardening influencers love to tout the benefits of DIY vinegar weed killer. It’s natural! It’s fast acting! It’s the safest thing for your garden! Videos sharing homemade weed killer recipes—usually a mix of white vinegar, salt, and dish soap—get millions of views. But do they actually work?
We decided to investigate whether vinegar can kill weeds or if it's a waste of time. For expert insight, we reached out to Clint Waltz, PhD, turfgrass extension specialist at the University of Georgia; Jeff Gillman, PhD, director of UNC Charlotte Botanical Gardens; and Stephanie Rose, author of The Regenerative Garden: 80 Practical Projects for Creating a Self-Sustaining Garden Ecosystem and Garden Alchemy. Scroll on to see what we found out.
How Vinegar Weed Killer Works
It turns out the truth is complicated. “Vinegar works by the contact method,” Waltz says. “The product only affects the plant tissue it touches but does not move systemically through the plant.”
After you spray a plant with a DIY vinegar mixture, the plant’s leaves will curl and wilt quickly. But this speedy response is misleading, luring you into thinking you’ve accomplished something. “Vinegar appears to be working right away,” Gilman says. “But after that, it’s an incredible waste of time because vinegar only disrupts the cells it hits but has no ability to penetrate the soil and roots.”
Sadly, that means most weeds start greening back up in 10 to 14 days, Waltz says. The reality is you’re not actually “killing” the weeds, just knocking them back—and then, not forever (more on that below).
Is Vinegar Weed Killer Safe?
There’s a perception that “natural” equals safe, but vinegar isn’t inherently harmless. “Some gardeners like the idea of using an ‘organic’ weed killer, but vinegar still is a chemical or herbicide,” Rose says. “It’s just not a synthetic herbicide.”
Vinegar also can harm creatures, including any beneficial insects, worms, salamanders, toads, or frogs hopping around in your garden. “Vinegar is toxic to amphibians,” Gillman says. “The idea that it’s in any way safer than conventional pesticides is ludicrous. Just because something is found in your kitchen doesn’t mean it’s somehow safe.”
After all, vinegar contains acetic acid. Household vinegar (the stuff you put on your salad) typically is 5 percent acetic acid, while stronger solutions, called horticultural vinegar, contain 20 or 30 percent acetic acid. These products can burn skin, cause permanent damage to eyes, and be harmful if inhaled, so manufacturers recommend wearing protective goggles and gear when using them. In fact, most states require EPA pesticide registration for the use of acetic acid as a weed killer.
How to Make Vinegar Weed Killer
You may have seen DIY vinegar weed killer recipes on social media using vinegar, soap, and salt. “From a horticultural standpoint, these recipes are laughable,” Rose says. “You’re really no better off than if you’d simply ripped off the leaves of a weed but left the roots intact. And in the end, you’re probably doing the same amount of work by spraying as you would have by physically weeding.”
And no matter what you’ve heard, these DIY vinegar weed killer mixtures aren't somehow “better” for your soil because you don’t see this concentration of acetic acid (or salt) in the soil in nature, Gillman says.
When to Use Vinegar Weed Killer
Vinegar isn’t totally useless, and it’s fine to experiment with it in your garden. “But understand what it can and cannot do, and adjust your expectations accordingly,” Gillman says. “If a weed is super small and has just emerged, it can work.”
Just remember that you will need to reapply vinegar frequently, about every 10 days or so, Waltz says. Vinegar also has no residual activity, so it doesn’t prevent new weed seeds from sprouting. That means you’re going to be out there a lot with your sprayer—which is fine if you've got the time.
Vinegar also works better on broadleaf and young annual weeds, such as broadleaf plantain and common chickweed, rather than grassy weeds like crabgrass. Vinegar doesn’t work well on perennial weeds, which return every year, Gillman says.
It’s also not useful for treating weeds that spread underground by tubers or stolons, such as nutsedge and clover, Waltz says. The vinegar won't contact these underground parts of the plant, so they’ll just keep coming back (and spreading).
Vinegar may work on weeds in gravel or between pavement or driveway cracks, though you should apply it in an inconspicuous area first to make sure it doesn’t stain the surface or damage the mortar after repeated use.
Finally, avoid getting vinegar on plants you don’t want damaged. Because vinegar is non-selective, it will harm any plant it comes into contact with, Rose says.
Long-Term Weed Management
A combination of approaches is the most effective and sustainable approach. In fact, weeds have a lot to teach us. “Weeds can tell us what we’re missing in our soils,” Rose explains. “When we have an attitude that we’re going to control nature, we create a system that has to be maintained in a very labor-intensive manner. But when we take a more holistic approach, we’ll have a better understanding of how nature works.”
For long-term weed management, try these tips from our experts:
Plant ground covers to prevent weeds from taking hold, Rose says.
Add mulch to keep weeds down in landscape beds and around plantings, Rose says.
Dig up weeds. “Honestly, pull the weed, and then you don’t have to worry about what you’re applying to your garden,” Gillman says.
Mow the lawns at the proper height for the type of grass you have, which will help suppress weed growth, Waltz says.
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