Homemade weed killers are all the rage and vinegar or salt or a combination of the two are highly publicized. How well do they work? How do they compare with Roundup? In today’s post I will compare the three options by testing them on real weeds in my garden.
Vinegar, Homemade Weed Killer
I’ve discussed vinegar before in Vinegar Weed Killer Myth. It is effective against small weed seedlings, and it does destroy the green leaves above ground. It has very little effect on roots.
In this post vinegar refers to the stuff you can buy in a grocery store. It does not include 20% acetic acid which is a dangerous chemical that does kill some weeds.
Salt, Homemade Weed Killer
Salt, usually in the form of sodium chloride, the table salt, is recommended quite a bit for killing weeds. It can be used in water, as a solid or even mixed with vinegar.
Salt does kill weeds, as well as all other plants. Sodium is a toxic metal ion which dissolves easily in water. It moves through soil along with the water. If the amount of sodium is high enough it kills plants, so it should be no surprise that it kills weeds.
Unlike synthetic or organic pesticides which break down over time, the sodium ion does not break down. It might be washed away by water to another location, like the soil where you grow favorite plants, or into local rivers and lakes, but it will always be somewhere.
Someone on a social network group said they kill weeds by applying salt, and nothing grows in the spot for at least 2 years. Great – the weeds are gone because the soil has been contaminated so much nothing will grow there until water leeches the excess sodium away. That does not sound like good gardening to me.
Roundup Weed Killer
The active ingredient in Roundup is a chemical called glyphosate. Contrary to popular belief, this is a safe chemical (ref 1) and it works very well on most plants.
Glyphosate is absorbed by the leaves of growing plants and is transported to the roots. There, it slowly kills the roots and in turn the whole plant dies. This process is fairly slow, and usually takes 10 – 14 days for the plant to die.
Roundup vs Vinegar vs Salt
The above descriptions are basic facts about the three weed killers. I wanted to see them in action and be able to compare them to see how effective they really are.
I know Roundup works since I have used it in the past on a few very stubborn weeds including quack grass and bindweed. I have never used vinegar or salt.
In early spring, I dug out some good sized dandelions and potted them up. I took good care of them for a couple of months to make sure they were growing well. The picture below shows the three plants just before being sprayed with a weed killer.
Each pot was sprayed once with one of these: Roundup, pickling vinegar (7% acetic acid), and salt (1/4 cup sodium chloride per liter water).
After treatment, all three pots were added to my nursery of potted seedlings, which are watered every day unless it rains. They received sun most of the day, with a bit of shade late in the day.
Two weeks after spraying.
From experience, I know Roundup takes about 10 days to start showing results. Plants are usually dead at the 2 week mark. It looks like salt also did a good job and that was not unexpected. Salt, at high levels, is toxic to most plants. Vinegar had browned off the leaves a bit after spraying, but new ones soon grew back. The vinegar treated plant is smaller than before spraying, but is growing fine.
Eight Weeks After spraying
Does Salt Kill Weeds?
You can see from the above picture that the salt sprayed on the plant was not enough to kill it. Things might have been different if the plant had been in the ground. Salt is very soluble in water, and more watering means that it is washed away quicker. The plant would not have been watered as much if it was in the ground and so the salt might have stuck around longer, in turn killing the plant. But that is just a guess.
The salt treated plant is not nearly as large as the vinegar treated plant. So salt certainly affected the dandelion more than the vinegar spray.
Salt may be better at getting rid of weeds, but it is just not a good idea for treating weeds in the garden. Adding salt to your garden is not good for your plants or the environment.
Does Vinegar Kill Weeds?
The pickling vinegar did do some initial damage to the leaves, but it clearly did not kill the plant. This is consistent with scientific reports that say vinegar at 5% or 7% have very little effect on weeds that have well established root systems. See Vinegar Weed Killer Myth for more details.
Vinegar will not kill most weeds in the garden. 20% Acetic Acid does kill some weeds, but is not effective on all types.
In my next post I test vinegar’s ability to kill other types of weeds Vinegar Weed Killer Myth Revisited.
Will Vinegar + Salt Kill Weeds?
Some recipes recommend a mixture of both vinegar and salt. This is probably more effective than just vinegar alone, but again salt is just no good for the garden. I would not use it.
Many of you will have trouble believing me when I say Roundup is less damaging to the environment than salt. Roundup degrades fairly quickly as bacteria and is converted to water and CO2. Salt stays in the environment for ever.
references:
1) Glyphosate technical Fact Sheet: http://npic.orst.edu/factsheets/glyphotech.html
2) All photos by Robert Pavlis
I read this entire thread with interest, although I am late to the party. Just because the WHO, or the EPA say that RoundUp is non cancerous, I for one doubt their sincerity. After all, both of these agencies fir in the “Big Govt, Big Business ” country club. They all scratch each others backs. I just dont buy it, or their test results.
So you would rather believe a stranger on the internet?
Hello, really enjoyed your gardening experiment and all the comments..
I too have tried and failed to kill weeds with typical white vinegar 5% acetic acid… So I decided to try Muriatic (i.e. Hydrochloric acid) acid from my pool supplies, full strength on a few weeds on my rocky walkway beside my house….. Not to worry.. Muriatic acid will react with all the limestone and river rock and not linger in the soil. However it is a much stronger acid than vinegar
At first it appeared that the muriatic acid did the trick, as it burned all the organic material… However within a month or so, the weeds returned.
My conclusion is that using acid does not kill the roots of weeds or invasive plants..
I am interested in any homemade mix that is effective and less toxic than Roundup.. Yet to see one.
That is because there is none. And many household chemicals like vinegar are more toxic than Roundup.
Hi Robert,thanks for the info.I did not see it mentioned in your article.My question is did you use a surfactant (like dishwashing liquid) with the vinegar spray or the salt spray?,that would make the vinegar or salt “stick” to the weed longer.
I did not.
Got it.Thanks for the quick response.
Boiling water kills weeds, too, and is cheap.
Actually it does not kill the roots of established weeds any more effectively than vinegar.
There are various theories as to why Sodium Chloride kills, but the toxicity of Sodium is not one of them. Toxicity has been identified as the increase in cellular levels of chloride, the displacement of other cations in the soil by sodium, and by lowering the availability of water and thereby dehydrating plants, or through hypertonicity which will cause cells to shrivel as water is drawn out of a cell All cells have very active sodium pumps that keep sodium levels low within the cell. Even salt tolerant archaea survive by pumping sodium out, and so it is unlikely that any toxic effect can be exerted in an otherwise healthy cell. Moreover Sodium is ubiquitous in the environment and an indispensable component of living systems. Sodium ion is not “washed away,” but is highly soluble in water and will diffuse through the environment, especially if you are watering your plants. “Washing away” is what happens to particulates, and sodium chloride is not a particulate when dissolved in water. When the concentration drops below highly concentrated levels, it won’t affect anything. You have made it sound like Sodium is a toxic metal which stays around doing damage. Far from it. Remove all sodium from an environment and nothing will survive.
You have also tested common vinegar which is not recommended as an herbicide by any source I have seen. The 20% form is recommended as an herbicide. The precautions would be similar to that used for Roundup. Moreover, if you do get some on you, just hit it with water and it will dilute down to vinegar strength quickly. Wear eye protection and long sleeves. It is no big deal.
You approach to addressing the concerns about Roundup typically involve ad hominem attacks against authorship which makes you sound like a virulent Roundup salesman. Monsanto sues people who grow crops using their seeds without paying royalties. The one case in which pollen was implicated was a lawsuit in the other direction – the farmer sued Monsanto for contaminating his crops, but failed to prove it. The commercial use of glyphosate lessens the overall application of herbicides to crops. In addition, there are overall economic benefits to farmers who use it. If you are not an organic farmer, it seems to be the way to go. However, is it necessary in a home garden? And your blithe dismissal of its suspected carcinogenicity is disingenuous. Having worked in chemical carcinogenesis research and watched its progress over decades, I will say this. Synthetic organic compounds, that are not natural products, are suspect from the start. If they are identified as a suspected carcinogen, that usually means they have a chemical structure similar to known carcinogens, and there is not enough data to address the hypothesis. Using Roundup on a garden exposes someone to such a compound, unnecessarily. When the data come back in twenty years, and there is or is not a statistical correlation, ask yourself if you want to be one of the test bunnies for Monsanto.
Organic farming is labor intensive and there is little evidence that it produces safer or more nutritious food, The produce is more expensive. Yet I buy it whenever I can, because I reject the assertion that increasing efficiency in the mass production of food has created a better world. It has collapsed the economic base of farming and concentrated control of it into the hands of a very few. It has created a world where food is so cheap it is wasted, and makes the soil and water sewers for every new experiment that comes down the pike. The GMO that increasingly dominates our crops is creating a monoculture world dependent on corporate control. The current state of affairs will also not last, as Roundup resistant weeds are being selected for and that will create a spiraling competition with natural selection that people will lose. And because some apocalyptic genetic accident has not yet occurred, there is clear evidence of the escape of these modified genes into the wild, and we are merely waiting for the extinction of some species because we want cheap popcorn or cotton T-shirts. In other words, 20% acetic acid, saturate it with table salt, and a few drops of dish soap and you will likely have something just as effective as roundup. And you can use it long after Monsanto goes belly up like Johns Mansville did for asbestos.
Keep in mind that this website is targeted to gardeners and not chemists. The actual mechanism of sodium toxicity is not that important, and maybe the term is used incorrectly, but it is the term best understood by the gardening community. also, even the scientific community uses the term, as for example in “Uptake of ubiquitous sodium ions is desirable as a way to build osmotic potential, absorb water and sustain turgor, but excess sodium ions may be toxic” in http://www.ncbi.nlm.nih.gov/pmc/articles/PMC139373/
The reason for discussing common vinegar instead of horticultural vinegar is that the majority of gardeners using acetic acid are using common vinegar. I never said ti was recommended as a herbicide – but it is what is being used and what is being constantly promoted in social media.
When WHO. The world health organization looked for evidence that glyphosate causes cancer they found none and labeled it as ‘possible cancer causing’. They looked at 50 years of testing. In the past year they have now stated that it does not cause cancer.
’16. After being regularly exposed to Roundup, two men who used Roundup for yrs have both developed non-Hodgkin lymphoma, a blood cancer that starts in the lymph cells. Both are plaintiffs in a suit filed against Monsanto that marks a turning point in the pitched battle over the most widely used agricultural chemical in history.
Until recently, the fight over Roundup has mostly focused on its active ingredient, glyphosate. But mounting evidence, including one study published in February, shows it’s not only glyphosate that’s dangerous, but also chemicals listed as “inert ingredients” in some formulations of Roundup and other glyphosate-based weed killers. Though they have been in herbicides — and our environment — for decades, these chemicals have evaded scientific scrutiny and regulation in large part because the companies that make and use them have concealed their identity as trade secrets.
Now, as environmental scientists have begun to puzzle out the mysterious chemicals sold along with glyphosate, evidence that these so-called inert ingredients are harmful has begun to hit U.S. courts.
So you see it’s not just glyphosate as you have failed to mention.
Roundup and Monsanto soon to be owned by Bayer are true detriments to safely and optimally grow agriculture. And since organic foods don’t have these from the get go toxins in them even though their nutritional value “may” be equal, makes them obviously less desirable.
The EPA and the World Health Organization have now both determined that there is no scientific evidence that Roundup causes any form of cancer. Just because someone is suing Monsanto proves nothing.
It is true the ‘inert ingredients’ have been studied less, but most cancer studies in field conditions used the whole Roundup product, not just glyphosate.
Organic food may not have these chemicals, but they contain lots of other natural pesticides. In fact in North America we eat up to 1,500 mg per day of these pesticides. https://www.gardenmyths.com/natural-pesticides/ Since we know almost nothing about these chemicals I would wory about them more.
For about 50 years, there was no proof that smoking caused cancer and a host of other diseases; but that’s because the tobacco industry spent billions of dollars burying evidence and buying scientists to falsify results. They finally were found out but for decades we heard there was no evidence. My money says the same thing is true of Roundup.
I am disturbed by your glib attitude about something being poured into the environment by the megaton.
It is not my “glib attitude”. I am simply reporting on information approved and verified by just about every organization including the EPA and the World Health Organization.
When people first starting smoking we did not know about the hazards – that was over 100 years ago. Science had proof about the hazards more than 50 ago – people just did not believe the scientists – they preferred to keep smoking.
What people seem to forget is that the herbicides that proceeded Roundup were much more toxic. Sure it would be better not to use any herbicides – but people won’t pay for that option – food prices would skyrocket.
I have to jump in, I can’t stand it. You are clearly pushing roundup as the safest way to go for killing weeds and it’s not toxic. I could care less about your research and trials that it does not cause cancer. Try talking to real people. I used roundup as a landscaper both at work and at home. It kills beneficial insects and I have advanced stage kidney cancer. I had dogs die of cancer. As far as using salt, vinager, and dawn it works!!!! I don’t spray it all over the property, I use it in areas where there is no need for weeds or plants and where my dogs go out to lay in the sun or do their business. I HATE roundup. You also mention that you spray it directly on the plant, we know that, but this gets very costly as other weeds pop up next to in in just a few days. AND for those of us that are getting too old to pull weeds every stinking day and have pets as our only companions…NO WAY IM GOING TO POISON MYSELF OR MY DOGS!
You are free to believe what you want – no one forces you to believe in science. But just because you believe – does not make it fact.
Non-organic/GMO agriculture is responsible for feeding millions of third world people all over the world. But feel free to feel good about yourself along with other wealthy enlightened “Whole Foods” consumers who won’t have to worry about starvation and other problems caused by poverty
Billions
Thank you Laplander, most excellent comment!!
One ‘weed’ I have very quickly killed with ordinary vinegar is a primitive horror called ‘liverwort’ (Marchantia polymorpha).
It grows like melted green wax on the ground in areas where the soil is moist and fertile and the air, humid.
Killing existing liverwort is only part of the solution however because it will grow back from spores if the underlying conditions for its existence are not altered.
PS I have really enjoyed reading the comments to this post.
I appreciate your test of vinegar. I am planning to try my own comparison on a gravel walk.I agree that Round-up works well in killing weed roots and has not been ruled a human carcinogen. But is inhaling Round-up safe? No, I am not ignoring directions. I live right next to a 50+ acre soybean/corn field that uses it generously at least 3 times a year. Even when the applicator is spraying on a still day (not that often) I smell it in the air for hours. I was told by an Ag Dept. rep that it can volatilize and drift up to a mile in hot still air.
You have to breath in a lot of Roundup before it would do any damage.
The perfume people wear is probably more harmful, and your morning cup of coffee is definitely more harmful.
Oh is it now? I want to see you drink a cup of round up instead of coffee for a couple of weeks (if you even make it) see if you change your opinion.
Just because something does not cause cancer does not mean we should be drinking it.
I want to play it safe for now, I’m trying to avoid using round up when possible. But if the job calls for it I will use it, we know it works very well. What do you think of using a weed torch. My plan this year is to use the weed torch in and around the garden. Will it work.
I have not looked at the weed torch in detail, but I suspect it has the same problem as vinegar. It burns the top green leaves and the root remains. I don’t see how it could possible damage a dandelion root that is 6 inches deep in the soil.
GREAT, I wish everyone would realize that any article needs to be researched and not just deemed true because it’s in print.
I am curious as to whether the 2.5 pH acid water produced by my batch-type water ionizer would be effective in killing the weeds that grow between the bricks and pavers on my patio.
I doubt it. If the low pH damages the leaves, they no longer work properly, and the root is saved. Herbicides work because they don’t damage the leaves. The herbicide is absorbed and spread through out the plant, and then chemical reactions kill the plant.
Not only that but your water isn’t really 2.5 pH.