Don't Pull Weeds and Grasses, Prevent Them! Introducing Roundup® Landscape Weed Preventer which prevents weeds and grasses for up to 6 months, Guaranteed!* It works by forming a weed barrier to stop weeds before they start. For best results, apply directly to soil around plants in Spring before weeds germinate and before mulching. Won't harm your desirable plants and flowers when used as directed! The easy to use built-in applicator provides even coverage. Now you can save time and energy with Roundup® Landscape Weed Preventer. A simple step towards a weed free landscape and garden!