When should herbicides be applied to effectively prevent germination of annual grasses?

Herbicides should be applied early in the spring to effectively prevent the germination of annual grasses. This timing is crucial because it coincides with the period when annual grass seeds begin to germinate as temperatures rise and moisture becomes adequate in the spring. Applying herbicides at this time allows the product to establish its effectiveness before the grasses can emerge and compete with desirable plants.

Using herbicides too late in the season, such as during summer heat or just before the first frost, would not target the early germinating seeds and may result in reduced efficacy. Additionally, late summer applications may not prevent germination as the seeds may have already started to sprout or will do so shortly thereafter. Therefore, early spring application aligns with the life cycle of annual grasses, maximizing the herbicide's intended use.