Only spray the weeds, not any plants. Choose a day without wind the product should not get into the soil soil. The spray will kill anything you spray so be careful. Follow all directions on the bottle. Get a jump on weeds early in the season. Preen works if you put it down before the seed germinates. It will not kill after that. Continue to add mulch yearly. As weed seeds blows on the mulch, they will germinate so putting down weed block mats will only help with the weeds underneath, not blown weed seed