Lawn maintenance usually requires attentive weed control. One of the most effective ways to control weeds is to apply pre-emergent herbicide, a chemical that prevents unwanted growth from appearing.Contrary to popular belief, pre-emergent weed killers don’t destroy weeds and their seeds. They simply stop them from growing. Some seeds are known to last fifty years, so if the herbicide isn’t applied each year, the weed will grow. The big question for pre-emergent weed killers is when to apply them. Pre-emergent herbicides only work if they are applied to your lawn before the weed’s growth period. But if applied too early, weather will dilute the herbicide and the weed will grow unencumbered.
According to garden experts from many regions of the U.S., the two dates to remember are March 15 and September 15. Those are the two dates of the year around which pre-emergent fertilizers should be applied so that they activate before seasonal weeds make an appearance.