When is a pre-emergent herbicide typically applied?

Pre-emergent herbicides are typically applied in early spring because this timing coincides with the germination of many annual weeds. These herbicides work by forming a barrier in the soil that prevents weed seeds from successfully germinating. Applying them at this time allows the active ingredients to be activated by soil moisture and temperature, which are optimal for the germination of both the desired grass and the weeds being targeted.

In early spring, conditions are generally warming up, and weed seeds that have been dormant in the soil during winter begin to germinate as they sense the changing temperatures and moisture levels. By applying pre-emergents during this period, turf managers can effectively suppress weed populations before they emerge and compete with established turf. This helps maintain the health and aesthetic quality of the turf.

For the other timings, while late winter is close to being appropriate, early spring allows for better effectiveness since weed seeds are actively pushed towards germination. Late fall and mid-summer would not be ideal applications for pre-emergent herbicides, as fall applications primarily target winter annuals, and summer applications do not align with the germination cycle of most typical weeds targeted by pre-emergents.