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The Garden FAQ Index |

Spraying weeds with vinegar?

LITTLE ROCK -- University of Arkansas experts say U.S. Department of Agriculture research that shows vinegar is a potent weedkiller could be good news for some homeowners and organic farmers, but it probably won’t result in farmers abandoning traditional herbicides.

Some home gardeners already use vinegar as an herbicide, and some garden stores sell vinegar pesticides. But no one has tested it scientifically until now.

Scientists with the Agricultural Research Service (ARS), a part of the USDA, say vinegar appears to be a potent weedkiller that is inexpensive and environmentally safe--perfect for organic farmers.

Researchers tested vinegar on major weeds -- lamb’s-quarters, giant foxtail, velvetleaf, smooth pigweed and Canada thistle -- in greenhouse and field studies.

They hand-sprayed the weeds with various solutions of vinegar, uniformly coating the leaves. The researchers found that 5- and 10-percent concentrations killed the weeds during their first two weeks of life. Older plants required higher concentrations of vinegar to kill them.

At the higher concentrations, vinegar had an 85- to 100-percent kill rate at all growth stages. A bottle of household vinegar is about a 5-percent concentration.

Canada thistle, one of the most tenacious weeds in the world, proved the most susceptible; the 5-percent concentration had a 100-percent kill rate of the perennial’s top growth. The 20-percent concentration can do this in about 2 hours.

John Boyd, weed scientist for the UA Cooperative Extension Service, says using off-the-shelf vinegar as an herbicide isn’t practical "unless you’re trying to kill small annual weeds. It’s not going to kill most big weeds or perennials."

Boyd said full-strength vinegar could be an alternative for homeowners who would rather not use chemical herbicides.

"It’s an alternative for non-selective weed control around the house, such as cracks in the driveway and weeds growing along the fence." Acetic acid is the active ingredient in vinegar that kills the weeds, Boyd said.

The ARS said spot spraying of cornfields with 20 percent vinegar killed 80 to 100 percent of weeds without harming the corn, but the scientists stress the need for more research. If the vinegar were sprayed over an entire field, it would cost about $65 per acre. If applied to local weed infestations only, it may only cost about $20 to $30.

Jeremy Ross, corn verification coordinator for the Cooperative Extension Service, doesn’t look for vinegar to replace farmers’ traditional herbicides.

"We’ve got stuff out there for weed control that has almost 100 percent control for only $20 to $25 an acre. There’s no way you’re going to get a farmer to spend $65."

Ross said organic farmers might be interested in vinegar as an herbicide. He noted that the major weeds the ARS destroyed in the research are broadleafs. He said farmers would apparently need another herbicide for grassy weeds.

The researchers said use only vinegar made from fruits or grains, to conform to organic farming standards.

May 24, 2002
Lamar James
Extension Communications Specialist
U of A Division of Agriculture

Credit for information from the following sources: Denver Botanic Gardens, MSU Extension Office, Colorado State University Cooperative Extension