Although it may sound like a good all-natural herbicide, vinegar can be hazardous and environmentally damaging.
Any gardener who cares about health makes an effort to avoid using chemical weed killers. Many organic farmers use vinegar as an alternative. Yet it is important to ask whether science supports the theory that the use of vinegar on plants is safe.
The active ingredient in vinegar is acetic acid. This ingredient can be produced naturally, through bacterial fermentation (apple-cider vinegar), or industrially, via chemical reactions from source materials like methanol. For concentrations strong enough to be effective against most weeds, the vinegar that should be used is not the type you would use on food. This type of vinegar is called horticulture vinegar, and it is not so friendly.
Vinegar is also a contact herbicide. This means it kills weeds within hours or days after touching them. Although this may look like an effective way of taking care of weeds, they, particularly perennials, will re-sprout form the roots quickly after being hit by vinegar.
Jeff Gillman, a contributor to the Garden Professors blog at extension.org and author of The Truth about Organic Gardening, is worried about this partial success. Since household vinegar does not work as well as anticipated, gardeners usually become dissatisfied, replacing it with a horticultural product (vinegar that typically has 20% acetic acid).
Despite the fact that there are several warning signs on most labels, some gardeners may only see the vinegar label and be careless. But it is important to pay attention to warnings because vinegar with concentrations of acetic acid over that are over 11% can burn skin and cause eye damage. Concentrations over 20% are corrosive to tin, aluminum, iron, and concrete, and can even cause blindness. If you choose to use horticulture vinegar, it is important to remember to wear goggles and protective clothing.
Use of this kind of vinegar is also dangerous to the environment because of its corrosive strength and ability to kill small animals.
If you are only looking to kill just-sprouted seedlings, you can use household vinegar to go after them right away. Otherwise it might be wise to reach for a hand cultivator than a spray bottle.
Instead of horticultural vinegar, you can rely on well-timed cultivation, and hand weeding. You can also rely on preventative mulches for support.
Ariana Marisol is a contributing staff writer for REALfarmacy.com. She is an avid nature enthusiast, gardener, photographer, writer, hiker, dreamer, and lover of all things sustainable, wild, and free. Ariana strives to bring people closer to their true source, Mother Nature. She graduated The Evergreen State College with an undergraduate degree focusing on Sustainable Design and Environmental Science. Follow her adventures on Instagram.