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
Yellow archangel has become very invasive on my property. It’s destroyed the amount of space for native wildflowers. I read that glyphosate is about the only thing that will kill it, and it has helped. I’ll be out again this spring spraying. It isn’t near anywhere that food is grown, nor adjacent to a body of water. And I don’t make my living going around spraying the stuff.I’m glad there’s a way to combat invasive species. (I’m in my late 60’s, and I’d say that spread over our not quite 2 acre property there are multiple large patches of the stuff – in the woods, etc, so digging it up by the roots just isn’t an option for me.)
From your own source posted above: “… a committee of scientists working for the International Agency for Research on Cancer of the WHO evaluated fewer studies and reported that glyphosate is probably carcinogenic.” Furthermore, some recent court cases seem to support that idea, as Monsanto was found guilty in connection with roundup and cancer. At least vinegar and salt does not cause cancer.
The court case proves nothing – it is just the opinion of the general public.
The court does not work that way or is the US just ruined?
How are you defining “that way”?
As much as I dislike Monsanto and glphysphate, now merged with Bayer, it works wonders getting pesky vines out of an area of the garden. I’ll wait a solid year while it breaks down before planting anything I’d eat but it is far better for the soil ecology than dumping tons of salt into the soil making it inhospitable to all plant life
After using RoundUp for a couple years I decided to switch to diesel fuel. Simple economic, RoundUp @ $12/gallon vs Diesel fuel @ $4/gallon. Super fantastic result.
And what kind of damage does diesel fuel do to the environment?
Hmmm… It came from the soil, it’s going back to the soil. Just like us one day. I wouldn’t think he is dumping a 50 gallon drum on his garden but a spray on the leaves?
Mmm, Monsantos paid research shows it as safe, too many reports refer to this research and go,on to rubber stamp its conclusions. Took a long time and some big compensation cases for the system to accept that there was a link between cigarettes and cancer. Also recently that the single piece of research referee to by US authorities concerning safety and the wholesomness of sugar was paid for by the sugar companies.
Untill I can find a piece of research that is new and genuinly not utilising others work, I will take any comment with regard to the safety of any Monsanto product with a pinch of salt.
There is already documented evidence that Glyphosphate used in the practice of ‘spray topping’ in the grain industry is being retained by the seed and plant material and ending up in the human dood chain, and straw from the crops that has been used in an organic setting has stunted growth of other plants. So may be itnis getting broken down quite in the manner we are being led to beleive.
I have a small holding and we will not use Glyphosphate anywhere near any food crops or on ground that is foing to be grazzed by animals destined for the food chain.
Huge thanks for this link Robert, really good lot of information 😀 I’m still having difficulty digging down to the evidence of consensus though – although the articles are very detailed, they don’t seem to be complete and thorough surveys of *every* study on every subtopic around glyphosate (well, the 3 I looked at aren’t anyway – I’ll have a look at the rest over the weekend!). There’s a lot of unreferenced assertions, and where he does provide links to studies it’s difficult to say whether he’s just cherry-picking to support his own opinions because a full list of relevant studies isn’t provided. Herein lies the problem I think- outside the particular scientific community on this (any) subject it’s very difficult to say what the consensus is, and it’s very difficult for outsiders to actually get a reliable handle on the full picture so we need to rely on “insiders” to guide us, but then there are all the issues of trust around that… But this guy doesn’t sound like an insider. I suspect his judgement might be as problematic as the soil association’s. That’s not to say I’m giving up on seeking knowledge, just that I tend to think we all just need to keep a totally open mind and always be mindful of the shaky foundations of what we think we know, given how mediated it all is through sources other than our own experience and experiment. Scientists themselves are very wary of stating anything as categorical fact. Im also very aware my own thinking and assessment of evidence is often flawed because I never took very well to critical thinking exercises at school 🙄 so Im totally open to being persuaded that my assessment here is wrong, if you feel so inclined 🙂 Thanks again- this is really useful stuff for me (I’m a newly qualified gardener) x
Thanks for your reply, and apologies – this is a more detailed summary of the research they’re referring to: https://www.soilassociation.org/media/7202/glyphosate-and-soil-health-full-report.pdf
I am very keen to get to the bottom of the situation because as you rightly say, the Soil Association is an organisation coming from a particular angle, so I wonder if you could point me to the source of your information about the scientific consensus? As I understand it, glyphosate environmental effects is an area of research that hasn’t yet been studied enough for a solid scientific consensus to be reached so it’d be interesting to see what you’ve seen 🙂 Thanks
This is one of the best, well balanced look at glyphosate.
https://thoughtscapism.com/2016/09/07/17-questions-about-glyphosate/
The soil association is a promoter of organic products that had their advertisements pulled from British TV because they were not true. Not an unbiased source.
More from the soil association: https://www.soilassociation.org/media/7229/glyphosate-and-soil-health-a-summary1docx.pdf
Statements like “As the efects of glyphosate on human health
come under scrutiny, scientists are now
concerned that we don’t know enough about
the ecological safety of glyphosate, how it
interacts with the natural environment and
living organisms, and what happens as it
breaks down” are only the opinion of a very small number of scientists. This is not the concensus.
The soil association has some interesting and well referenced things to say on the glyphosate issue: https://www.soilassociation.org/our-campaigns/not-in-our-bread/glyphosate-research-and-references/
This is hardly an unbiased source of information.
For example they forgot to mention that another group at WHO concluded that glyphosate is not a carcinogen. Nor did they report that IARC in reaching their conclusion ignored a large amount of research data.
Regarding torching weeds, as i understand it you don’t want to incinerate the weed, merely burn off the “hairs” so the stoma won’t close, so moisture loss is continuous, resulting in death by thirst. Probably more effective in drier climates than humid ones.
Never heard that before. So a lack of hairs on a plant prevents stomata from closing? I don’t buy that.
Hi there
I read your article on vinegar/salt vs roundup. I am an organic gardner and I agree that the only way that killing weeds will work with vinegar/ salt (and I use dawn detergent too) is applying it over and over again. I have a lot of Bermuda grass which is almost impossible to kill so I do use this mixture often to some success.
My argument with you is RoundUp. Glyphosates are NOT good for us. They kill not only weeds but are harmful to pollinators, like bees, and are responsible for killing them in droves as well as other factors that bees have to contend with. Also, this chemical has been proven to cause cancer. It shows up everywhere ( in honey for example and breast milk) and in California we are making Monsanto label this chemical as cancer causing.
So please do not suggest to people that RoundUp is safe because even though it is successful in killing weeds it is also successful in killing beneficial insects and possibly causing cancer in all of us.
Thanks
Your understanding of glyphosate is completely wrong. There is no evidence it causes cancer and several of the world’s largest governmental organizations have reached that conclusion, along with most scientists.
California has a stupid law that requires just about everything to be labeled as a carcinogen, including Disney World and the power cables for computers.
It has also been banned by several countries. When in doubt with your health, it’s better to wait and see how the controversy pans out before putting yourself and your family at risk, if you can. Look at the HPV shots, for example. They were sure these shots were safe, only to find out later that they were not.
In the case of Round Up we are way past a wait and see period. It has been around so long we now know.
Vaccines are safe, glyphosate is safe. Enough with the ignorant fear-mongering.
How do you reconcile your “safe” claims to the research that Roundup causes Non-Hodgkin Lymphoma and the lawsuits most recently a $6+ million in Roundup settlement?
The lawsuit tells us nothing about safety. There is no scientific evidence of Roundup causing Non-Hodgkin Lymphoma – you are listening to online nonsense.
Glyphosate doesn’t kill bees(in concentrations used to spray weeds), your older generation nicotine-based ones (aka “natural”) kill bees.
Also, applying a little bit of salt at a time over a period of time, that eventually become toxic to your plant, is the same as dumping a lot of salt over a short period of time, your end result is unhealthy, salty soil.
I think Monsanto is a terrible company, so don’t think for a second there is any loyalty to them. However, my opinion aside, their product is not something evil… even if they might be.