Vinegar is a cheap, natural product that can be used for many household tasks, especially in the garden. Apple cider vinegar and white vinegar are environmentally friendly weed killers that can be used directly on the weed or the surrounding soil. In fact, Sweden lists vinegar as a registered herbicide for controlling weeds on sidewalks and pavements.
Vinegar contains acetic acid, a natural weed killer. According to Purdue University, "USDA researchers confirmed that acetic acid is effective at killing some common weed species, including Canada thistle, lamb's-quarters, giant foxtail, velvetleaf and smooth pigweed." Most vinegar has a relatively low percentage of acetic acid, because it is typically used in the kitchen and for cooking, so be prepared to reapply as necessary, or look for a horticultural vinegar with a higher percentage of acetic acid.
pH of soil
The acetic acid in vinegar lowers the pH of the soil, preventing weeds and other plants from growing. Saturate the soil with vinegar to destroy current and any potential weed growth.
Applying vinegar to the weed
Vinegar can be used to directly spray weed foliage. Spray apple cider or white vinegar on the plant to destroy the protective coating and leave the weed vulnerable enough to dry up all the way to the root. This is especially effective in the early stages of growth; according to Purdue University, "The researchers found that 5- and 10-percent concentrations killed the weeds during the first two weeks after emergence from the soil." Most household vinegar is 5 percent acetic acid.
Destroying the root
Remove as much of the weed as possible by hand, and then pour full strength distilled vinegar on the remainder of the weed to kill it. Use vinegar directly on the root or soil to penetrate to any remainder of the weed.
Vinegar will destroy grass, lawn and weeds. Selectively spot-treating weeds with vinegar will kill the weed without harming desirable plant life. Use vinegar in areas such as the sidewalk or driveway, where you do not want grass or weeds to grow.