Pre-emergent herbicides represent a huge step towards weed control. Quick and easily-applied, pre-emergents act on seeds and seedlings. They basicly contain enough noxious chemicals to kill the fledgling weeds and plants without hurting exisiting ones. Pre-emergent herbicides are becoming hugely popular and have been developed more and more user and plant friendly. The original pre-emergents were fairly loaded and somewhat toxic to existing plants. However, more research in this field has resulted in pleasing results to the end of chemical weed control. Inasmuch as most are also hosed into the ground, thereby forming a gasous vapor for such small plantlings, pre-emergents disappear into the ground are are non toxic to animals.
I use them at the completion of almost every project. After completing these fairly impeccable scenes, the last thing one needs is an invasion of noxious weeds and plants. We spray at the completion, then offer the service in ensuing years as well. Most herbicides are good for 6 months, preventing any weed growth in places not desired. I usually spray in Spring and midsummer. Preen, Surflan, Ronstar are among the names many are familiar with. New products are always coming online as well.