BioSafe Weed & Grass Killer is a non-selective herbicide that works on contact when applied as a foliar application. This OMRI Listed product works on perennial and annual broadleaf and grass weeds in two ways: as a control and for burndown suppression. Plants that produce spores, such as liverworts and mosses, will also be controlled. For best results, use on weeds before they mature and cover plant leaves thoroughly and uniformly with spray. Take care to avoid contacting wanted plants. Within 1-2 hours of application you will begin to see it working; the plant's foliage will turn from green to brown or black. This soap product penetrates the cell walls of the plant to disrupt their normal functioning and cause death; the browning of the leaves is due to this necrotic plant tissue. This product does not move through the soil or between plants and leaves no harmful residue.