Salt and vinegar are delicious on chips, but did you know you can use salt and vinegar to kill weeds? It does, though, need to be mixed and applied the right way that is proven to work, without, of course, the chips!
There are many weed killer recipes that combine vinegar with salt, and sometimes dish soap and/or Epsom salts. You can also use undiluted vinegar in small doses.
Can vinegar actually kill weeds?
Does vinegar kill weeds? There is considerable debate about this, but the general consensus is, yes it can. The best results are on young weed plants that have germinated recently.
At the same time, it depends to some extent on the type of vinegar you use. If you make your own weed killer using vinegar, it also depends on the ratio of vinegar in the mixture.
The U.S. Department of Agriculture’s (USDA) Agricultural Research Service (ARS) offered the first scientific evidence that we can safely kill weeds with vinegar. That was way back in 2002, and they maintain that not only is vinegar an environmentally safe and inexpensive weed killer, but it is also perfect for organic farmers.
Three ARS researchers hand-sprayed weeds with different vinegar solutions using only organic vinegar made from grains or fruit. Jay Radhakrishnan, John R. Teasdale, and Ben Coffman tested their potential weed killer vinegar on several major weed types, in a greenhouse, and in field studies. They were Canada thistle, common lamb’s quarters, velvetleaf, smooth pigweed, and giant pigweed,
Despite their reported success, others disagree. Marisa Y. Thompson, extension horticulture specialist at the New Mexico State University Los Lunas Agricultural Science Center, is one of them.
Commenting on the ARS research, she warns that many weeds in her area develop a waxy cuticle that protects the leaves and prevents the vinegar from being absorbed by the plant.
Also, vinegar isn’t translocated from leaves to the roots of perennial plants, including Canada thistle, horsetail, and dandelions. This means it only burns the tops, and the roots or rhizomes below the surface of the soil will quickly re-grow. She does, though, concede that if you treat them often enough, you may eventually kill weeds by depleting the food reserves stored in the roots.
The ARS researchers were able to kill young weeds no older than 2 weeks with 5-10% concentrations of vinegar. Older plants needed higher concentrations of vinegar, and the success rate ranged from 85-to 100% during all stages of growth.
Amazingly, Canada thistle, which is one of the most tenacious weeds, turned out to be the most susceptible to the vinegar weed killer.
Household vinegar with a 5% concentration of acetic acid had a 100% kill rate of the top growth of the thistles. When they used a 20% concentration, it worked in only 2 hours.
They also spot-sprayed weeds in cornfields using 20% solutions of vinegar, which is the strength of horticultural vinegar you can buy at home improvement and garden supply stores. This killed between 80% to 100% of the weeds without harming the corn. At the time they said it would cost about $65 to spray an acre. If they only applied the vinegar to weed infestations, it could cost as little as $20-$30 per acre.
Ultimately, the 3 researchers stressed the need for more studies. A primary reason for this is because the acetic acid in vinegar causes rapid burn to the plant tissue of any susceptible species that we may not want to harm.
What type of vinegar to use?
Ordinary household vinegar is not intended for use as a herbicide. As mentioned above, typically, it contains 5% acetic acid and can be effective for weed control.
Two types most of us keep for use in the kitchen are:
- White spirit vinegar, which is clear and made from grain
- Apple cider vinegar, which has a golden brown color and is made from apples
You might have red or white wine vinegar too. This is also a natural product made through fermentation, like the others, but from grapes. It is, though, a lot more expensive than other types.
Horticultural vinegar has a minimum 20% concentration of acetic acid and it is intended for use as a pesticide. You will find that it is labeled as a weed killer! Most importantly, it is not intended for human consumption.
The caveat is that any vinegar solution with more than about 11% acetic acid can burn the skin and cause eye injuries. So, it’s essential to follow the precautions on the label. And if you concoct your own recipe that contains a greater percentage of acetic acid, you must be aware of the risks.
An Environmental Protection Agency (EPA) fact sheet on acetic acid, in general, acknowledges that “Pesticide products containing acetic acid are used in controlling a diverse group of weeds, including some grasses.” More specifically, it targets many perennial and annual broadleaf weeds and grasses.
The fact sheet states, “There are no risks to the public or the environment when the active ingredient is used according to the label. However, applicators are required to use protective equipment to prevent contact with skin and eyes.”
Vinegar Weed Killer Recipe – Make Your Own
There is no doubt that a weed killer that contains 20% acetic acid vinegar will work better than a household vinegar that contains only about 5%. But, if you’re going to mix your own, rather use what’s safe to consume.
Here are a few recipes you can try.
Mix 4 cups of 5% household vinegar with 1 cup of salt and ½ teaspoon of liquid dish soap.
The soap helps to dissolve any protective coating on the leaves and makes it stick better to the plant. The salt will help to dry out the root system of the weed.
Mix 1 gallon of vinegar with 1 cup of salt. Do not add this mixture directly to the soil.
Mix 1 gallon of vinegar that has 5% acetic acid with 1 oz. dish soap.
Mix 1-gallon vinegar (white 5%) with 2 cups of Epsom salts and ¼ of a cup of dish soap.
Undiluted household vinegar on its own can also do the trick but is only cost-effective if you’re zapping a few small weeds.
Steps on how to apply vinegar weed killer
The EPA advises that the best way to apply acetic acid vinegar weed killer is to spray it onto weeds early in the season when there are only a few leaves. They warn that the product must contact the leaves to be effective.
Only apply vinegar weed killer in sunny weather when there is no chance of rain. Also, don’t apply it if it’s windy because the wind can end up spraying plants you don’t want to kill.
Mix your concoction and pour it into a spray bottle that is set to a stream rather than a wide spray. You could also paint it onto the plant. Pouring it into the soil will affect the quality of the soil, but might be a good topical option for weeds like Canada thistle.
Get up close to your weeds and spray to cover the entire plant.
Repeat when and if the weeds start growing again.
How long does vinegar take to kill weeds?
It often looks as if a dish soap vinegar or any other homemade weed killer works within hours. But, it’s not so much a case of how long it takes vinegar to kill weeds, but rather whether they will grow back again.
For instance, a 5% acetic acid vinegar + Epsom salts + dishwashing soap homemade weed killer will likely kill thistle shoots quickly, usually within 24 hours, but they are likely to grow again.
How much vinegar do I need to kill weeds?
The exact quantity of vinegar you will need will depend on the recipe you use and the volumes you want to mix.
Other home alternatives
Boiling water is another popular option for killing weeds in a home garden. But, like vinegar, it will kill any plants it comes into contact with.
So, if your weeds are scattered in garden beds or veggie gardens, where other plants are growing, hot water is not a good idea. If you can be selective, it could be a great idea.
Ordinary table salt is another common DIY solution, which is why some of our home remedies include salt. It can work well, but if you use too much, it can negatively affect the condition of the soil.
You can use salt on its own, diluted in water and sprayed onto weeds, or as part of a vinegar-based weed killer.
Salt is best used to control weeds in paved areas like driveways, patios, and various other walkways.
Ultimately, the most effective method is pulling weeds out by hand. A lot of weeds have a very shallow root system. If they don’t come out easily, use a garden spade or fork.
Vinegar is a great ingredient for a natural weed killer, but many home gardeners find they need to repeat the process many times for it to work permanently. Still, it’s eco-friendly and comes with zero risk.
If you decide to use horticultural vinegar, be sure to follow the instruction on the label to the last letter.