What is the difference between pre-emergent and post-emergent herbicides?

Pre-emergent herbicides are specifically designed to prevent weed seeds from germinating. They create a protective barrier in the soil that inhibits seed development and rooting. This means that these herbicides need to be applied before the target weeds begin to sprout, making timing crucial for their effectiveness. They are typically used in early spring or fall, depending on the type of weeds and the climate.

In contrast, post-emergent herbicides are applied after the weeds have already emerged and are actively growing. They work to kill existing weeds by being absorbed through the leaves and moving throughout the plant, ultimately resulting in its death.

This clear distinction highlights why the accurate answer focuses on the prevention aspect of pre-emergent herbicides, whereas the other options do not accurately describe the functions and applications of these herbicide types.