Good old white vinegar right out of your kitchen cabinet is more than just a tasty salad condiment. It's also a 5 percent acetic acid solution, powerful enough for a 100 percent kill rate on some of North America's toughest weeds. Cheap, effective, readily available and environmentally friendly, this completely natural homemade assault weapon does have one small flaw. Vinegar weed killer isn't a fussy or selective assassin--it kills petunias as quickly and efficiently as it decimates pigweed. Just be careful where you spray it.
Combine ½ gallon white vinegar with 1 ounce liquid hand dishwashing soap. A killer in its own right, soap breaks down the protective covering of many weeds, making them more susceptible to the effects of the solution. It also allows the solution to stick to foliage better by breaking the water tension. Another plus is that it causes the leaves to look shiny even after drying, so you can easily see areas that you've already treated.
Pour the vinegar weed killer into a hand sprayer, 1-quart size or less. The smaller the sprayer, the more control you'll have over exactly where you're directing the herbicidal spray.
Apply the vinegar weed killer during the hottest part of the day, or when the most direct sun is available. Coat all surfaces generously with the solution. Vinegar serves as a desiccant by sucking moisture from plants, and bright sunlight enhances this capability.
Reapply to more resistant weed plants in about three days.
Label and store unused vinegar weed killer in a cool, dark location.