Does vinegar really kill weeds? It is commonly suggested as a chemical-free weed killer, and a natural alternative to commercial herbicides, but is this true? Let’s find out what the facts show.
If you are interested in misleading gardening advice, these garden myths have been causing trouble for years.
Does Vinegar Work as an Herbicide?
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Is Vinegar Really a Harmless and Effective Herbicide?
Check any online gardening forum and as soon as someone asks for a way to kill those weeds on their brick patio, there’s a dozen people saying, use vinegar! Add Epsom salts! And dish soap! Or, use them all together!
The implication is, that vinegar is a smart, safe, and natural choice. Because, if it’s in our kitchens, it must be okay for the garden, right?
But is this good advice? Let’s just look at the vinegar today.
What is vinegar? Is it really harmless? Does it kill weeds?
Vinegar is acetic acid, made by fermenting ethanol or sugars.
There are different concentrations, depending on the type of vinegar.
The vinegar you have in your kitchen will probably say “5% acidity” on the label.
Some brands also sell a “cleaning vinegar” which is 6% acid.
Pickling vinegar can get you up to 7%, and that’s probably the highest concentration that you might have at home.
What Vinegar Does to Plants
Vinegar (acetic acid) is a non-selective burndown herbicide. In other words, it burns plants.
Just like an acid would burn your skin, it destroys cell membranes.
And not just weeds, but any plant or living thing it touches.
But, depending on the concentration and the weed itself, this does not mean it kills the whole plant. Vinegar can only burn the parts it touches and unless it gets right down where the roots are, it is not going to kill the plant, which is what we want.
Instead, it does temporary damage.
Related: Popular Garden Myths
Spraying Household Vinegar on Weeds
Vinegar burns the plant parts it comes in direct contact with.
In contrast, selective herbicides (various commercial products made for killing weeds) are designed to be absorbed by the plant, spread to the root, or disrupt some other systemic function, which kills it off.
Vinegar can burn and kill very small weeds, but not larger ones.
Tiny, tender seedlings with shallow roots don’t stand a chance, but those larger weeds like crabgrass that sit proudly in the cracks of our brick patios with roots deep in the ground are not giving up so easy.
Gardeners are sometimes fooled because, after spraying vinegar, they notice the leaves dying back and assume the entire plant is dying, but often it’s just leaf burn and the roots are still alive. The plant is temporarily knocked back but it will return with a vengeance.
Related: 7 Weeding Tips Every Gardener Should Know
To be an effective herbicide, you need a 15 to 25% concentration of acetic acid. This is sold as horticultural vinegar, but this is not the vinegar you’ve come to know from your fish and chips.
Horticultural vinegar is dangerous stuff and not suitable for home use. It is a highly corrosive acid, and absolutely not worth the risk of burning yourself or causing damage.
But, will it burn weeds?
Yes: it will burn anything it comes into contact with. But we started this whole conversation because we want harmless, chemical-free* ways to deal with weeds, and this does not check any of those boxes.*I’m using ‘chemical-free’ the way it’s used in garden forums (implying toxicity) not science since obviously everything in our world is comprised of chemicals.
Related: Is it Safe to Reuse Potting Mix?
What Else Are You Spraying?
Watch where you spray!
If you insist on trying household vinegar in the garden, be careful. It burns everything it touches and that includes all living things like frogs, toads, and salamanders which experience agonizing burns.
Any other insects and microbes it touches are also wiped out.
Household vinegar is a chemical (acetic acid) and not ‘natural’ or harmless.
It is non-selective, meaning it burns everything it comes into contact with: plants (weeds or not), and living things from animals to microorganisms in the soil.
And this does not make it a good weed killer.
Small weeds with shallow roots may be killed. Or not.
Most large or deep-rooted weeds will get their foliage burned and gradually grow back.
Horticultural vinegar is too dangerous for use at home, and neither natural or harmless.
But it worked for me!
If the vinegar got the roots, then yes, you scored root death.
Most likely though the plant will rebound in the weeks to come so you can do this all over again.
Other Non-Toxic Weed Removal Options
There is this curious assumption in the gardening world that there must be a solution for every problem. And sometimes it comes with a tone of entitlement, as if we should be able to control nature exactly to our liking, no matter what overall effects ensue.
But if you wish to grow a garden without doing more harm, this just is not so.
Sometimes we have to accept problems—and most are temporary anyways—or accept less than perfect solutions.
Weeding in general is much easier when done after a good rain that loosens the plant roots. You can read all my top weeding tips here.
For weeding a brick driveway or pathway, I have found something that seems to work quite nicely without having to hand-pull the weeds for hours.
I use my home steam cleaning machine to kill the weeds on our driveway. It’s much easier than taking out pots of boiling water because one session provides 30-45 minutes of steam, and I can work standing up.
I was skeptical, but it really does get down to the roots, even with the crabgrass. If you go to the article you can see a video of how it works.
Keep in mind though that just like vinegar, boiling or steaming water is going to kill tiny living things it touches, so I would not do this anywhere but on a brick pathway.
If you do manage to truly kill off or remove the weeds (roots and all), consider adding polymeric jointing sand to the cracks to prevent new seeds from germinating there.
If you are wondering about other popular garden advice, click here for more on household items like dish soap, Epsom salts, eggshells, coffee grounds, and more. And spoiler alert: there’s little or no research to support many of the claims.
Keep safe out there and be kind to our earth,
~Melissa the Empress of Dirt ♛