Author: Ellen Jacquart
The accounts I’ve heard of people using vinegar as an alternative to other herbicides to combat invasive species have intrigued me. I was willing to give it a try after learning that vinegar, or acetic acid, is efficient in eliminating some common weed species, such as Canada thistle, lamb’s quarters, giant foxtail, velvetleaf, and smooth pigweed, in a 2002 report by USDA researchers.
In this investigation, weeds were manually sprayed with a range of vinegar solutions to evenly coat the leaves. The weeds were found to be killed in the first two weeks after emerging from the soil at 5- and 10-percent concentrations. Higher vinegar concentrations were necessary to destroy older plants. Vinegar showed a death rate of between 85% and 100% at the higher concentrations for all growth stages. The roots of permanent weeds, such Canada thistle, survived and continued to grow, only being briefly knocked back. You may get more details on the USDA study online here.
I had to give it a shot on my own. I paid $6.45 at the neighborhood farm co-op for a 24 oz. bottle of BurnOut, a weed and grass killer with 6.25% acetic and ethanoic acid (table vinegar has about 5% acetic acid). I reasoned if it didn’t work, at least the woods would smell clean and fresh, so I mixed some vinegar and lemon juice.
I chose to test it against garlic mustard, a biennial, because the USDA research made it plain that perennial weeds are only top killed. I treated a number of second-year garlic mustard plants that were just beginning to bolt in the beginning of April. The plants that had been treated completely withered after an hour. And sure, the air did have a really energizing scent. However, when I looked on the plants two weeks later, they were in bloom. Every plant was able to fully recover and blossom after the apparent transient wilting in reaction to the treatment.
It should be noted that using vinegar products to kill weeds is prohibited by federal pesticide laws unless they are expressly labeled as herbicides. Always read and abide by the instructions on any pesticide label.
– Image of a BurnOut bottle next to a garlic mustard plant (photo credit Ellen Jacquart)
How may garlic mustard be killed naturally?
The most effective method of eradicating garlic mustard when infestations are minor is by hand removing plants. Remove plants before they flower early in the season. Also, remove plants when the garlic mustard weeds are young and the earth is moist, making sure to extract as much root as you can.
After removal, tamping the ground will aid in preventing the regrowth of the plants. As part of your garlic mustard weed control strategy, if it is too tough to pluck the plants, you can cut them as near to the ground as you can before they produce seeds.