How to use vinegar on weeds

Q. I’ve heard about people using vinegar to kill weeds. Is this ok to do? Is it organic?

Shirley from Austintown

A. Yes, vinegar is a registered herbicide. But only a few products are technically labeled for use in Ohio.

USDA conducted a comprehensive research project in the early 2000s to determine the role for vinegar as an herbicide for organic farmers. The study reviewed different percentages of acetic acid (the acid in vinegar) and how effective different percentages were in killing weeds.

Before going further, you must understand that vinegar is a non-selective herbicide. This means it will generally kill or ‘burn down’ the top of any weed that gets enough of the spray on its leaves. Additionally, spray drift from using a vinegar herbicide can kill plants. Thus, care must be exercised when spraying the product – just like any other herbicide.

Your household vinegar is about a 5 percent concentration of acetic acid. This rate will kill top growth on certain plants. For example, in the study, there was 100 percent top-growth kill of Canada thistle. This means the growth above the ground, but not the roots. A gardener will need to spray multiple times to kill all of the roots under the ground. In the case of Canada thistle, this may be multiple times over more than one year to get rid of all of the roots. The roots store food (carbohydrates), and these reserves allow for new shoots to emerge. Continual removal of top growth eventually will deplete root reserves.

For some annual weeds, control is usually permanent if the weed is controlled at the right stage. When it comes to control of weeds, smaller weeds are easier to kill. Bigger weeds are more difficult to control.

Just like other herbicides, you must be careful with application. Concentrations above this 5 percent threshold can be harmful and can “burn” exposed skin upon contact or by drifting in the wind. When used as a weed control option, vinegar is in fact an herbicide and has a toxicity level just like any other herbicide. Speaking in technical terms, acetic acid (vinegar) is more toxic than glyphosate (aka – Roundup).

Use of vinegar to kill weeds should be done only through purchasing vinegar that is a registered herbicide and contains label information with specific rules for use. Always read and follow label directions before purchasing and prior to use.

To learn about research and burndown of weeds in a Cornell study, go to http://go.osu.edu/vinegar; to learn about the research study on vinegar as an herbicide, go to http://go.osu.edu/vinegarresearch.

Eric Barrett is OSU Extension educator for agriculture and natural resources in Mahoning County. Winter hours for the Plant and Pest Diagnostic Clinic vary. Submit questions to the clinic at 330-533-5538 or drop samples off at the Extension office in Canfield.