Homemade Organic Weed Killers


When it comes to organic weed killers that work, there are a few options. One option is a homemade organic weed control recipe that's rolling around the Net right how and I thought I'd check it out.

Test One


This recipe calls for combining vinegar and salt at 1 gallon of vinegar to 2 cups of salt plus a half-cup of a cheap cooking oil. 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.

organic weed control
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

thistle burned by organic weed control
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.

aegopdodium burned by organic weed killer
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.

Updates


I have experimented with this homemade organic weedkiller for several years after I wrote this original report. The addition of soap is critical while the salt is helpful but not critical. The oil does seem to help and I use the cheapest cooking oil I can find at approx 1 cup per gallon of vinegar.

My normal spray now doesn't use salt.

Current Recipe


  • 1 gallon of vinegar (minimum of 7% acetic acid. higher is better)
  • 1 cup of vegetable oil
  • 2 tablespoons liquid soap


  • It takes several burns to kill off perennial plants and sometimes several years (can you say Aegopodium?) to really whack the plant to the ground. It took 4 years to wipe out the Aegopodium. It might have been shorter but I did allow it (stupid me) to recover strength a few times in the second year. When I got serious in year 3, it pretty much disappeared by year 4. Year 5 was clean.

    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, Soap and Salt as an Organic Weed Killer?


    Yes, it does have the ability to burn off some plants and some people consider it a good organic weed control combination.

    No - it is not useful on lawns where you're concerned about overspray and burning off grass as well.

    Caution: Do wear protective breathing masks when spraying these products - whether you mix them yourself or purchase commercial equivalents. The tiny spray droplets are quite acidic on lung tissue.



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