Early Spring and Fall are the most effective times to apply pre-emergent herbicides. They can be applied throughout the year, and will still prevent new weeds that sprout, however most weeds sprout during spring and fall.

How often can you spread pre-emergent?

‍Every product is a bit different. Typically, you can expect one treatment to last 3-5 months. However, Canopy recommends applying a split application approximately one month apart to maximize effectiveness. It is also important to select a good product.

What happens if you apply pre-emergent too early?

As long as you are early enough, as mentioned before, there is no harm in getting the pre emergent down way ahead of time. It just might wear out too soon to get the later batch of weeds if you start too early.