Keep garlic and vinegar for a salad, do not use them for weeds in a garden

By Bev Johnson

Master Gardener

In 2006, the University Of Minnesota decided to test organic weed killers against Round Up and Finale. They laid out 2×2 foot squares of lawn grass that had a few dandelions here and there. The area was in full sun. It had been seeded two years earlier with mostly Kentucky blue grass and smaller quantities of fine fescue and perennial ryegrass. 

The plots had no warm season annual grasses and almost no broadleaf weeds in the plots. The soils were generally of a medium soil texture. That is, no heavy clay or mostly sandy soils. To make it fair, there were also plots that were not treated. The plots weren’t irrigated although it did rain during the testing. All the plots were mowed with the mower set at 3 inches. 

The products evaluated were all acquired at local stores. Four were organic and 2 were chemical.

1. All Down Organic Grass and Weed Killer. The active ingredients in this one were 5 percent Citric acid, 2 percent garlic. Other ingredients were Acetic acid Yucca Extract and water to make up 94.8 percent.

2. Ground Force Organic Herbicide. The active ingredients were 10 percent Citric acid, and 0.2 percent garlic extract. The 89.8 percent left consisted of vinegar, yucca extract and water.  

  3. Burn Out 11- weed and Grass Killer. The active ingredients were 4 percent Clove Oil and 3 percent Sodium Lauryl Sulfate. 93 percent consisted of vinegar, Lecithin, Citric acid, mineral oil and water.

  4.  Everything Must Go. The active ingredients  were 10 percent Citric acid, 5 percent garlic oil 1 percent Lauryl sulfate and the other 84 percent, acetic acid and water.

The two chemical products were Round Up Weed and Grass Killer and Finale.

1.  Round Up has 2 percent glyphosate and 2 percent pelargonic acid and other fatty acids. No other ingredients were listed,

2. Finale lists 1 percent Gluconate ammonium as active ingredients and doesn’t say with the other 99 percent are.

All of the sprays were in ready to use sprayers.  All of them were applied 3 times at 2-week intervals. The weather was sunny to mostly sunny with temperatures ranging from 75 to 85. Soil moisture was considered a bit on the dry side although it wasn’t measured. All the plots were green and looked healthy.

The first week, all the organic plots showed very rapid browning and drying of the grasses within 24 hours, with the exception of Everything Must Go. It only damaged the tips of the grass. RoundUp damage wasn’t as obvious, and Finale took about 4 days before damage to become really evident. By the second week, all the organic plots had improved significantly, the grass getting greener. The dandelions were still showing damage. They didn’t look as good as the control plots, however. The two chemical weed killers had killed all the vegetation their plots. The Everything Must Go plot had completely recovered and had a normal green color that was no different from the control plot. By three weeks, all the organic plots sported nice healthy green grass and dandelions. The 2 chemical plots were brown. Seven weeks later, there was no change in any of the plots. The 2 chemical plots were still totally brown and dead. The organics showed no damage and had nice thick grass and blooming dandelions.  

The scientists were not surprised by the test results. They felt that since the organics were considered contact herbicides, the active ingredients weren’t taken up by the roots of the plants as the chemical killers were.  The moral of the story is keep the garlic and vinegar for your salad, not your weeds.