A while ago I wrote about using vinegar as a weed killer, in Vinegar Weed Killer Myth and reported on the scientific evidence for vinegar weed killer. It does not kill larger weeds with established roots, but can have an effect on seedlings. Vinegar is recommended so much in social media that I decided to give it a try myself.
I ran a few simple experiments to see how effective vinegar is for killing weeds.
Vinegar Weed Killer
In this post vinegar refers to the stuff you can buy in a grocery store. I decided to use pickling vinegar with a 7% acetic acid concentration. Around here it is the same price as the 5% strength, so you might as well buy 7%. Besides it might work better.
This post does not discuss 20% acetic acid which is a dangerous chemical that does kill some weeds.
Homemade Weed Killer: Vinegar
So vinegar kills some weed seedlings, but mostly it just burns off the green parts above ground. I was curious to see how effective it is. It might be a worthwhile product to use on a patio where a lot of the weeds are seedlings.
I just happened to have some weeds in my patio. OK, I always have weeds in my patio, but I have a garden open house in two weeks and need to remove them to make people think that I am always weed free.
Before Pictures:
People claim that the weeds “die within hours” of being sprayed. After a few hours I saw some browning, but not very much. I decided to wait until the next day before taking the following pictures.
24 Hours Later
The weeds in the sprayed area do look quite dead. The green ones in the top and upper right corner of the picture were not sprayed.
You can see that some of the smaller weeds have brown leaves, but the larger weeds seem to be unaffected. So I gave them a second good soaking.
After Second Spraying
The vinegar did not do a good job on the large weeds. Even after several days, they had some green leaves. I ended up removing them by hand before the open house just to clean things up.
Eight Weeks Later
It is now mid August, and the above picture shows the area where the small weeds were sprayed. They did not regrow. The one large weed is a crabgrass that has recently grown from seed. I have to admit, it was more effective than I expected. I can understand why people claim vinegar kills weeds.
Vinegar vs Crabgrass
The above experiment showed that vinegar does kill small seedlings. By mid August the spaces between my flag stone pathway was full of crabgrass. I wondered if vinegar could be effective against crabgrass?
I used the same pickling vinegar as in the above experiment, and sprayed the pathways.
Before Pictures:
Not all of the weeds in the pictures are crabgrass, but many of them are.
After Pictures (24 hours after being sprayed with pickling vinegar):
The plant leaves are certainly brown, and to the untrained eye – they look dead. The green weeds in the upper left corner of the closeup view are weeds that did not get sprayed.
If you get real close to the weeds, as in this next picture, you will see that the crown of the plant and the stems are still green. For the most part, only the flat blades of the leaves were damaged by the vinegar, and then only the ones that got into direct contact with the vinegar.
A week later, and the weeds were growing back with new leaves. They were not killed by the vinegar.
Vinegar is a Contact Herbicide
The above pictures show that the vinegar only affects the parts of the plant it contacts. That is consistent with the scientifically reported mechanism for vinegar. It affects the cell membranes of a plant, causing rapid breakdown/desiccation of foliage tissue on contact. It is a contact herbicide only damaging the green parts it contacts. The rest of the plant, and especially the roots are unaffected by the vinegar. This explains why it is not a very good herbicide for larger plants.
I use a combination of two gallons of white vinegar, half round box of genetic salt and a few ounces of dish soap mixed in a garden watering can , does great on weeds. And I don’t have to worry about my well water
Except the vinegar does not kill weeds – you get the same effect with just salt which kills everything in the soil if you put in enough.
Hello,
Can I spray the 30% vinegar on the weeds that are growing on top of our mulch? Will it bleach the mulch?
Thank you
I doubt it would bleach the mulch, but even if it did – so what?
Except it kills my weeds. Wonder what you’re doing wrong?
Nothing. Even the scientific studies have shown it does not kill established weeds – only small seedlings.
I also live in southern Ontario. I have a 2 story maple tree that keeps invading my plumbing system and it’s roots punctured through my basement foundation wall. Can see the roots sticking out of the wall.
I’m assuming that you have to cut it down to a stump before applying any type of poison to it in order to kill it? Would digging and exposing the roots and then applying a poison like blue copper or rock salts to the roots work without having the cut the whole tree down?
Or could just drilling a hole into the side and putting Gordon inside the tree work? Would prefer to not cut the whole thing down and just let it die
copper and rock salt won’t kill a tree – or the roots.
You can’t kill the roots without harming the tree.
If telling garden can you spray vinegar solution without harming future planting
Did you mean tilling? First of all – don’t till – it is not good for soil. Vinegar is a contact herbicide that only affects the green parts of plants it comes into contact with. It is quickly decomposed in soil by bacteria.
I have been using agricultural vinegar, which is 30%, for several years on poison ivy and English ivy. The plants were pervasive and some of the English ivy looked like it was going to kill the trees. I can report that this stuff is very effective against these robust weeds. I just wish it were not so expensive. It does cost $25-30/ gallon.
Have you ever used 30% commercial grade vinegar and salt brine to kill poison ivy or would just plain salt brine kill poison ivy?
Thanks Robert for getting back to me. I planned to spray the area multiple times to deprive the plants the ability to produce chlorophyll. I have cleared the area as good as I can and trimmed the plants to approx. 5 inches. Painting the individual plants with Round-up really isn’t practical. There are hundreds of plants. Thanks again Robert.
I have done thousands of buckthorns the same way. Paintbrush in one hand – pruner in the other. It goes quicker than you think.
Hi Robert,
I don’t want to wear out my welcome, so one last question. When you say paint the stem with Roundup, do you mean just the cut area of the stem or the whole thing? I really appreciate your spending time answering my questions!! Thanks Robert.
Paint just the cut surface. In fact all you need to do is paint the thin inner bark that transports the glyphosate to the roots. I put some Roundup in a kids beech pail. Dip a 4 inch brush in the liquid, and do a dozen stems. Then recharge the brush. It is quite quick, but you are bending over the whole while. I usually do an hour or so at a time, and then find some other work to do.
Oh thank you on that!! We have a one block wide 3 blocks ling enpty area full of weeds. Our yard gets all sorts of seeds each wind. We are trying to kill off plum tress taking over our back yard as well as wood vine. I’ve learned a lot reading through all your posts. Thanks.
Hi Robert,
I need to kill off some black raspberry plants that were located under a weeping willow and evergreen tree. I have cleared the area and cut down the plants to approx. 4-6 inches in height. My question is, if I used 20% vinegar, will it harm those trees? If so, do you have any ideas? They are taking over my yard.
20% acetic acid will not harm the trees as long as you don’t get the spray on the leaves/needles. But it will probably also not kill the raspberries. They have large root systems. You can try spraying every 2 weeks to brown off any new leaves. Eventually this should work. Alternatively, wait until mid summer, and cut the stems back to 5 inches, and paint the stem with roundup. This will do a good job.
Hi, sorry for hijacking this item but I’m curious as to whether or not you have an opinion regarding using sprouting store bought potatoes over certified seed potatoes. Cheers
I only tried growing potatoes once – they just take too much space and are real cheap in fall. I used old sprouted potatoes that worked fine.
It is probably best to use certified potatoes since they are certified to be disease free.
Thank you for that article. You explained the effects on the plants from the vinegar, is there any affect on the soil? Residual, etc
Since vinegar is acidic, it will tend to make soil more acidic – but that really depends on how much vinegar you use, and the nature of your soil. If you have alkaline soil that alkaline because it contains limestone rock, as my soil does, the vinegar will not change the pH of the soil. I suspect that for most people the amount of vinegar used will have very little affect on pH.
The acetate molecule in vinegar is a molecule found a lot in cells of all types, and is a food source for bacteria. It won’t linger long in soil, and have a very limited affect on the soil.
To understand the acidification of soil better, have a look at this. https://www.gardenmyths.com/increasing-soil-acidity/
If vinegar (acetic acid) is used regularly, it’s possible that the pH of the soil will be changed as a result. And using salt as an herbicide will add sodium and chloride ions to the soil — not a good thing. I have used a flame weeder — basically a propane torch designed for the purpose — to control small weeds growing within a path that has open jointed stonework — bluestone, brick, etc., with good results. Doing it at dusk (making it easier to see the flame) and having a hose at the ready (just in case, but it’s not particularly dangerous if common sense is applied) is a good idea.
I enjoy your examinations into conventional horticultural wisdom, and into plant nomenclature/identification. Hope that fence between Canada and the US that Scott Walker is now talking about won’t prevent the export/import of empirically-based information.
I have not looked at flaming in detail, but it seems to be a workable solution. I’m not sure how effective it is at getting to the ‘root’ of the problem.
I expect that the change to soil pH would be very limited. https://www.gardenmyths.com/increasing-soil-acidity/
I did not know who Scott Walker was – so I Googled him. The first link said “Canada Also Thinks Scott Walker Is A Idiot”. I did not read teh rest of the article. http://wonkette.com/593553/canada-also-thinks-scott-walker-is-a-idiot
Read more at http://wonkette.com/593553/canada-also-thinks-scott-walker-is-a-idiot#ZA0hIqJPRmk43XW8.99
I am going to try a combination of three organic approaches; vinegar, occulation, and flameweeding. I am trying to kill grass and weeds on an area that was previously lawn and will now be 3×50 foot garden beds. I only have enough landscape fabric to do a few beds at a time but the method would be to spray the vinegar, cover the grass with a tarp, then burn the dead/dying grass in a few weeks with a torch. I will have to lightly till the soil to form the beds, which I imagine will bring up some weed seeds but a once-over with the torch and a stirrup hoe should kill those quickly. Keep up the good fight!
Don’t use landscape fabric. I have found no good application for the stuff in the garden.
I don’t understand the logic behind this method. Vinegar and flaming do about the same thing – destroys the green part of weeds. I think flaming may work better than vinegar at killing some roots. There is no point in flaming after spraying with vinegar. The tarp will kill weeds but it does almost nothing in just two weeks. You would need to leave it on for a couple of months, depending on the type of weeds and temperatures.
An expert gardner in San Antonio, Bob Webster passes on his Vinegar weed killer.
One quart of 20% Vinegar, one tablespoon of Orange Oil and 1 teaspoon of dish soap. Mix well, will be milky color…Don’t shake as soap will foam up. Used best in a spray bottle with mist/squirt tip.
It works so well nothing might grow there for a few years….
Is that 20% vinegar or 20% acetic acid – there is a huge difference between the two. Standard vinegar is 5% acetic acid, so 20% vinegar is 1% acetic acid – that won’t even taste good on fries! Let alone kill anything.
20% acetic on the other hand is a very toxic chemical and it has been shown to kill some weeds – but not all kinds.
I have not researched orange oils a lot – but they also are a leaf burn type of product – they don’t kill roots.