Concentrated vinegar is used for natural and organic control of broadleaf weeds. Vinegar is most effective if liberally sprayed on target weeds while they are in direct sunlight, and preferably during the hottest part of the day. Repeat spraying may be necessary to eradicate deeply-rooted weeds. Concentrated vinegar may used to spray lawns, but a test patch is strongly recommended. Spray a small area of lawn and observe, the grass may turn yellow, but should return to green within a few days. Likewise, most flowering plants will be affected, especially those with a broad leaf. Protect these plants while spraying.