Organic Weed Killers
Test One
This recipe calls for combining vinegar and salt at 1 gallon of vinegar to 2 cups of salt. I did this and sprayed it around on a variety of test plants.
The results were not particularly surprising given the nature of the combination. There was a significant amount of leaf spotting and burning where the material had laid on the leaves. None of the plants was killed outright and all have rebounded as expected if you’d burn off the tops but not kill the roots.
The damage was limited because the spray didn’t go on evenly (see test 2 below).
Plants with thick leaves (Aegopodium) were not bothered very much at all - no wilting or check in growth and only a slight discoloration of the leaf surfaces. Dandelions seemed the most sensitive as they curled up and browned off - I note though that these were the most heavily sprayed.
As a general rule, the thinner the leaf, the more damage was sustained. Grass was burned off with full coverage.
Test Two
I decided that part of the problem was the lack of a surfactant - something to spread the spray and enable it to cling to the leaf without puddling up and running off. So I took a few tablespoons of dish detergent into the next test. Same 2 cups of salt to gallon of vinegar.
The results were different. The dandelions were totally burned to the ground (see picture) These will regrow. This isn’t going to be a lawn treatment as you’ll also kill the grass around the dandelion as well. Grass also browned off.
Burned Dandelions in Bark Chipped Pathway
The mature thistles I sprayed started wilting within a half hour of spraying, looked quite ill at 5 hours but at 18 hours had rebounded to upright with burning and spotting on the leaves. Not a kill at all for this highly touted organic weed killers
Burned Thistle from Organic Spray
Virginia Creeper and Sumac were not touched although the leaves are heavily spotted.
The Aegopodium is severely burned but not wilting or looking like it has any intention of laying down and dying. This was heavily sprayed.
Damage to Aegopodium from organic weed spray
Crown Vetch has been burned including the flowers that were in full bloom.
Bottom Line
It has a variable impact on leaf surfaces in my trials depending on the plant. The thicker leaved and aggressive growers seem to be the least bothered.
Environmental Impact of Organic Weed Killers Using Vinegar and Salt
It is well known that salt has a negative effect on the growth of plants (the Romans pretty much took care of the Carthaginian Empire by salting their fields after the third Punic war)
The problem for us is the long term effect of salt. It is washed down into the ground water by rains and in some areas and climates, this is going to be a problem.
Vinegar (acetic acid) is being used by itself in stronger concentrations in commercially available herbicides to burn off plants. These products work quite nicely while household vinegar by itself has a limited effect on plant leaves.
Can I recommend Vinegar and Salt as an Organic Weed Killer?
Well technically no I am not able to recommend using this kind of product. In my garden, I won’t use it. I don’t like the potential of salt in the soil and ground water and it’s certainly not a registered product.
It also has a limited effect on plants I want to get rid of in my garden.
I prefer the acetic acid or other more effective products that clearly do the job of burning off leaf surfaces on a wider range of plants.
And given the ease of mulching gardens and a bit of hand-weeding, this kind of burning product has a limited use in my garden. Remember, you can’t use if on lawns without killing the grass around the weeds as well.
But yes, it does have the ability to burn off some plants and some people consider it a good organic weed control combination. But no, because of the variablility in effectiveness I won't be using it.
Got a Question about Vinegar as a Herbicide
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What Other Visitors Have Asked About Vinegar as a Herbicide
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Vinegar and salt
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