What is a pre-emergent application?

At the beginning of each spring season the first application made will be what is referred to as a pre-emergent application.  You may have heard it referred to as crab grass preventer as well.  If applied correctly, yes it will prevent crabgrass.  However, that application can prevent many more weeds than just crabgrass.  

The pre-emergent timing is a very important factor in if your application is effective.  The product, which can be of granular type or liquid, must also be watered into the soil by at least.25-.5” inches of irrigation or rain.  The timing must be BEFORE the crab grass and other weeds have germinated.  Hence the “pre” or “before” in the name pre-emergent.  

A skilled applicator will be aware of the soil temperature ranges at when the product should be applied.  

The homeowner must not rake, or bag any grass clippings from the treated area until it has been watered sufficiently.  Effectively you want to leave the product where it is until it has had a chance to be watered in.  

So at this point we have had our application and it has been watered in.  So what exactly does it do?

The pre-emergent product forms an invisible barrier at the soil surface.  If a weed seed gets enough water, warmth and sunlight to germinate as soon as it attempts to root into the soil that root will be burned or “pruned” and the weed will die before becoming established.