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
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
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
As a general rule, the thinner the leaf, the more damage was
sustained. Grass was burned off with full coverage.
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
The Aegopodium is severely burned but not wilting or looking like it
has any intention of laying down and dying. This was heavily
Damage to Aegopodium from organic weed spray
Crown Vetch has been burned including the flowers that were in full
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.
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.
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.
Resource for High Potency Vinegar
You can now buy 20% vinegar by the gallon for serious weed burning
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