Vinegar

Vinegar makes for great pickles and salad dressings, but can it kill weeds? Let’s find out!

We’ve all heard the story - spray your weeds with vinegar and they die. What a great idea! And so easy! But does it really work? First, let’s learn a little bit about vinegar.

Vinegar is not the weed killer you've heard about

What is vinegar?

You know it when you smell it or taste it. There is no mistaking the tang of vinegar, or the smell of decorating Easter eggs. Vinegar is a sour, acidic liquid made from fermented low-alcohol liquids, such as beer, wine, or cider. The acid in vinegar is called acetic acid. The vinegar you buy in the grocery store is 95% water and 5% acetic acid. When the concentration is 8% or higher, it must be labeled acetic acid. Some people call this higher concentration horticultural vinegar, but I find that label misleading. It is not vinegar. Vinegar is food, while acetic acid is a potentially dangerous chemical. The difference between the two matters.

Pickles (PhotoMIX) Pixabay

Acetic acid as herbicide

To be used as an herbicide, commercial agriculture uses a 20% concentration of acetic acid while wearing protective clothing. Acetic acid is a contact herbicide. This means it must come into contact with weeds to kill them. Acetic acid acts by dissolving cell walls, which allows fluids to leak out. This dries out the plant, potentially killing it. This method is more effective on younger plants and those with thinner skins. Tough, woody plants are more resilient, resulting in a burned appearance while remaining alive. Repeated treatments are often needed to kill off tenacious perennial weeds. Unsprayed parts are not affected. Plants accidentally sprayed are affected, as with any chemical overspray.

You cannot buy acetic acid at the grocery store, but you might find it at a garden center. If you decide to use acetic acid to clear out some tough weeds, do not use your aluminum sprayer. Acetic acid will damage aluminum and iron surfaces.

As with any pesticide, it should only be used on plants listed on the label, and it the manner described in the instructions. And be sure to wear eye protection and other personal protective equipment (PPE) when applying acetic acid.

Chemical Hazard symbol (The Navigators) Public Domain

Vinegar as herbicide

If you spray weeds with household vinegar, the aboveground portion of the plants might dry up and die. Or, it might not. It will not affect the root system. By the time the vinegar filters through the soil to reach the roots, it will have gone through chemical changes that make it practically harmless. And what do weeds do when you kill off the aboveground portion? They come back, again and again, ready to produce thousands of little weed seeds. 

Of course, if you treat weeds repeatedly with vinegar, you will eventually force the plant to use up all the food stored in the root system, killing the plant. Probably. But honestly, it would have been simpler to just cut it off or pull it out in the first place.

Let’s stop sharing these myths about vinegar in the garden and leave it in the kitchen where it belongs.

That being said, if you have a bad sunburn. try gently wiping the affected area with a cloth soaked in vinegar. You might smell like a salad, but it won’t hurt anymore. I have no idea why.