Description Kill the toughest weeds and grasses down to the root with Roundup ready to use weed and grass killer III refill. The formula is ideal for use in and around vegetable gardens, flower beds, tree rings and mulched beds, as well as on cracks in driveways, walkways and patios. This convenient, no-mix formula is rainproof in just ten min. And you get visible results in 3 hr. Simply pour into your any ready to use Roundup weed and grass killer III applicator and kill weeds faster with Roundup.