“When should I apply a premergent crabgrass barrier to my lawn?” We receive this question in the form of emails and phone calls every Spring. Some go by when the forsythia is blooming, others by a date, and some by soil temperature. All these are fairly good indicators it is a good time to apply your premergent barrier to the lawn.
We begin our 1st lawn treatments, a premergent crabgrass barrier or corn gluten meal, in March and go through April applying them. We monitor the soil temperature during the Spring. This is what you should be looking at. You can monitor your soil temperature in Ohio on this website
The goal is to get your premergent crabgrass barrier down before the soil temperature reaches 50-55 degrees consistently. If you use higher quality premergents, like Purelawn does, you can continue to apply this type of crabgrass barrier later in the Spring while still being effective.
Corn Gluten Meal
Try putting your corn gluten meal down before you see the spring weeds popping up. This is usually about the same time as your chemical premergent barrier.