Once I started doing that I cut the weeds. Preen not only cleaned them out last year but this spring we still have very few that have grown. Preen Weed Preventer Review In 2021 Grass Killer It can help clear dandelion and clover ultimately. Preen weed control reviews . 8 of 8 people found this review. Last Spring We used Preen to kill the dandelions that had taken over the yard. The product can also get the lawn to grow stronger and healthier. Since I started using Preen I have more time to spend with my kids and less work pulling weeds. In conclusion Preen is mildly harmful to the environment like many weed control products. This year I have significantly more weeds. We give it 4 Dandelions instead of 5 - only because of it being a chemical pesticide. Our Preen review results. I previously had used preen for years and had been satisfied with the product efficacy and safety. I learned in the first couple years to pull those pesky weeds that start coming u...