Preen® Garden Weed Preventers control grass weeds and other weeds, feed plants and help yield a neat, professional landscape. The Preen® solution to garden weed control is keeping weed seeds from germinating and growing. Grass weed killers are not needed because Preen® keeps the seeds from sprouting. Preen® weed and feed products nourish plants while eliminating the need for a garden weed killer. There’s no need to kill weeds when Preen® prevents them!