White vinegar makes an excellent earth-friendly herbicide. Just spray the vinegar full strength onto weeds, making sure they’re well doused. This works best on a sunny day (The acid stops the plants from absorbing moisture if it’s warm and sunny) The plants will turn black in a few hours.
The vinegar doesn’t work well on deep-rooted plants, but it is excellent in eliminating those tiny reseeding plants that plague gravel and flagstone paths and patios. After a number of applications, fewer and fewer plants will grow in the areas you want to keep plant-free. Vinegar also performs well on moss growing on brick and stone paths and patios.
Use vinegar with caution, however. Test it first on a small area of pavement to make sure it doesn’t discolor it or, in the case of limestone, dissolve it. Also, when vinegar is used repeatedly it raises the acidity of the soil to the point that it can render a patch of ground temporarily sterile (an advantage in paths and patios where you don’t want anything to grow). And finally, make sure none of it drifts over onto other, desirable plants. Use a piece of cardboard or a sheet of newspaper to protect nearby plants, if necessary.