Monday, August 4, 2014

My Non-Scientific Vinegar Weed Killer Experiment

My "Driveway".  Yes, that weed strip down the
center is growing on a gravel driveway.  It is green in
August because I had my tomatoes on top of it
(moved to the left in the image).
I have an old gravel driveway.  I don't think it's been re-graveled during the entire life of the house. If you
have one of these driveways, then you probably also have weeds.  Lots of weeds.  Well, you'll have lots of weeds if you're loath to use conventional herbicides on your driveway as I am.  In the past, I've used a propane torch to burn away the weeds and it did work well, but lugging around a small tank and flaming weeds in the hot sun was not fun.  I've read of using vinegar to kill weeds.  Some articles claimed good success.  Others poo-poo'd it to some degree.  I finally decided to give the vinegar recipe a try after discussion of it stumbled onto my Facebook feed.  The ingredients are cheap, so why not try it on my driveway?

Here is the recipe I used:

  • 1 gallon of distilled white vinegar.
  • 2 cups Epsom salt.
  • 1 tablespoon of dish soap.
The ingredients and sprayer that I used.  Brand is not
important.  I'm not endorsing any particular brand.
Photo edited by my talented wife.
The vinegar and Epsom salt are supposed to work by desiccating the weeds.  The dish soap is a wetting
agent to prevent the vinegar/salt mix from beading up on the leaves.  The solution will be more effective if it spreads evenly over the leaf surface.

To optimize success, there are some things to keep in mind if you want to use this formula to kill your weeds.
  • Vinegar/salt weed killer is a broad-spectrum contact herbicide.  It will kill only the parts of the plant that it touches and it will not discriminate between weeds and  your beloved garden plants.
  • Most weeds you kill WILL come back from the roots.  Some weak-rooted annuals may not return.  If you keep re-applying this recipe often enough, you might wear down the stronger weeds over time, resulting in fewer and fewer returnees.
  • Apply this mix when the weed foliage is dry.  Applying to wet foliage will dilute the spray as it lands and may reduce it's effectiveness.
  • Vinegar/salt weed killer will be more effective during hot, sunny weather.  I applied it on a sunny day with temperatures in the low eighties.  I'm curious to try it out in cooler weather when the weeds make their comeback.
  • Wear eye protection!  Safe or not, vinegar and salt still sting like hell when they get in your eyes.
A comparison of treated and untreated weeds two days
after applying the vinegar/salt weed killer.  Treated weeds
are on the left, untreated on the right (obviously).
Within half an hour after applying the spray, I noticed the dandelion and catsear leaves beginning to curl and turn dry.  Within two hours, most other plants were showing symptoms.  Within two days, the success of the spray was very apparent (see photo).

I must say I'm happy with the results so far.  I will have to reapply repeatedly.  It will be interesting to find out how well this method works for me in the long run.

A driveway dandelion three days after the vinegar.  Just wait
until next weekend.
Now, as I write this it is three days after I applied the vinegar/salt spray on my weeds.  Already I am seeing regrowth of the weeds (see bottom photo).  But that is not unexpected.  It is a trade-off for using a cheap, supposedly safer, herbicide.  I have used Round Up professionally, and I will say that it is definitely a more effective herbicide (the weeds stay dead).  The upside of using this vinegar/salt mix, however, is a far less guilty conscience whether the guilt is justified or not. 

So far, my experience with this recipe has been good.  I'm very curious to see how it works on my winter batch of driveway weeds when it is cooler and dry days are rare. 

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