I’ve read about the pre-emergent herbicide PREEN. It sounds like it’s quite effective, but does it persist in the environment/flower bed?? Does it harm the soil and/or the plants/perennials you're growing?? And, most importantly (for me, anyhow), is it harmful to pets??? (cats, in particular)
There are a couple different formulations of Preen. One contains only corn gluten as the active ingredient. The other uses the chemical trifluralin as the active ingredient. If you're concerned about pesticides, you may want to choose the natural corn gluten formulation. Trifluralin has been in use for decades and is considered quite safe.