Roundup Weed and Grass Killer Concentrate Plus, 36.8-Ounce Kills the toughest weeds and grasses to the root. Guaranteed! For use in a tank sprayer For use around flowers, shrubs and trees; on patios, walkways, driveways, gravel areas and mulch beds; along fences, edging and foundations; as well as large areas such as lawn replacements or garden plot preparation. Not for use around existing edibles. Rainproof in 30 minutes Visible results in 12 hours with FastAct Technology