Spring Pre-Emergent:  How Does it Work?

If you have been with a lawn and landscaping service for a while, you are probably aware that the first rounds of fertilizer and weed control include something called a pre-emergent.  

What is it?  Simply put, pre-emergent is a weed killing chemical, but the primary difference between that and a post-emergent, as you can imagine, is that pre-emergent kills the weeds before they germinate.

However, it is important to note that you cannot apply pre-emergent at any time during or before the spring.  For it to be effective, there are a few factors to consider before either spraying it on your turf or even if it is combined with a simple granular application fertilizer. 

  1. Consider the temperature. 
  • A pre-emergent will not be effective at colder temperatures because it may break down without penetrating the soil before it has a chance to activate during the germination process. For best results, apply when soil temperatures are at least 50 degrees. 

2. In order for it to work, pre-emergent must be watered in. 

  • Now, that does not mean you need a sprinkler system. Rainfall of half an inch will suffice if you cannot water it in yourself before seven days after application. 

3. In general, keep in mind that most pre-emergent will not work on some broadleaf weeds like dandelions. 

  • The main weeds controlled by pre-emergent are destructive and unsightly grassy weeds such as crabgrass (Always read the label to know what kind of control you will get). 

4. After temperatures reach a certain point pre-emergent will not be effective because most weeds have already germinated by then. 

  • The idea is to have a layer of protection before they start growing. One caveat: Not all pre-emergent are equal in what they control or their effectiveness. Always read the label.

One final note:  if you are seeding in the spring, you cannot apply pre-emergent because it will kill the seeds that have or will be put down; pre-emergent must be given at least eight weeks to penetrate the soil after application before seeding. If you plan on doing spring seeding, wait until the fall or the next spring to put down pre-emergent (or, better yet, consider seeding in the fall). As you can see, a lot of timing is involved when getting the most out of weed control, which can seem overwhelming without experience and the free time to take care of it. If you are feeling overwhelmed or just want more free time, call Lightning today at 913-441-3900 and let us take away the worry.