Preventing weeds is easy with the right product. Waterloo Gardens carries several different varieties of Round-Up to suit your needs, including pre-emergent for easy weed prevention. Block weeds in your garden beds with Preen or Osmocote. To prevent crabgrass on your lawn, be sure to put down Scott's SuperTurf Builder with Halts. If you already have weeds, Roundup is a complete herbicide and will terminate everything.