Q. What product will kill weeds but not flowers?
Dear Gardener: If you apply Preen, a product that prevents seed germination to the bed, the weed seeds will not germinate. However, if you are planning to plant seeds for your flowers, rather that buying plants, don't use Preen as the flower seeds will not germinate. The other method to prevent weeds is to mulch the bed. The mulch will prevent the weed seeds from germinating and will help the flowers by helping to hold the moisture in the soil. The mulch also will improve the soil as it ages.