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Know When to Overseed with Pre Emergent and Post Emergent Herbicides

By DoMyOwn staff

Overseeding your lawn will depend on your grass type, the type of seed you are laying down, and your pre and post emergent application timing.

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Video Transcript


As we get ready to head into spring, a lot of people are going to be looking to overseed their lawns and wondering when they can put a pre-emergent down, if they can put a pre-emergent down, as well as post emergents for those pesky winter weeds that may be popping up already.

I'm Amber with DoMyOwn and today we're going to dive into overseeding with your pre and post emergent applications. Let's dive into the details and we'll talk all about it and make sure that you've got the best-looking lawn heading into the spring and summer. It's really important to take in consideration not only what type of grass seeds you're going to be putting down and the timing of that over seeding that you may be looking to do but also your pre and post applications in general. 

How long after putting a pre-emergent down can I over seed my lawn this is going to depend on the particular product you're using. You'll want to reference the product label to make sure that you're well outside that pre-emergent barrier window and make sure that you're putting it down at a time that the grass seed actually has a chance to succeed. This is normally going to be a minimum of three to four months so this may actually push you outside of your seeding window to where you have to do it the following season. 

How long after over seeding can I apply my pre emergent herbicide? This is going to be entirely dependent on the timing of year. However, the general answer is going to be you're going to need to wait until that grass has come up completely and is actively growing and has been established for at least four to six weeks or has been mowed a minimum of two times. Every lawn is going to be different. 

For cool-season lawns, typically seed is going to take best in the fall. This means spring pre-emergent applications normally aren't going to be a big problem for you. You can do them like normal and be able to prevent all those spring weeds from coming up later in the summer months. If you have a lot of fall in winter weeds that you're seeing coming up in your lawn now and you normally see it in the fall, you're going to need to take into consideration putting a pre-emergent down instead of seeding for the coming season to help get rid of those weeds and help you have a better looking lawn for the following year. For those who decide to take that step and put a pre-emergent down in the fall, you do still have the opportunity to overseed a little in the spring while the turf may not take quite as well as it does in the fall. 

For those cool season blends like fescue and Rye and bluegrass, they can still establish with a little extra love. 

For warm season grasses, a lot of customers are going to be putting that down in the spring rather than fall. Warm season grasses are going to be things like Bermuda, St. Augustine and zoysia, for instance, and those turfs are going to thrive under those high heat temperatures,which putting them down in the spring just the ideal time and it makes sense. 

Now post emergents. This is one that can get kind of tricky. Most herbicides in general post emergent or otherwise are going to need to be done on an established lawn.

Now you'll want to consult your product label just like we mentioned before. Everything is contingent on what that chemical has the ability to do and what turf grasses its label to be used on and when. 

Some will allow you to use them when the turf is still kind of dormant, some you have to wait until it completely is in a fully growing and active state later on in the season. For instance, some products out there like Quinclorac products, will allow you to apply them at seeding or very close to seeding without having any risk of damage to your turf type. 

Most other post emergents on the market are going to need at least a several week window just like your pre emergent window of four to six weeks. 

After that turf has come up and everything's been established and mowed. The only time that you're going to have an exception to that is if the product label says so. 

To all you DIYs out there, good luck on your lawn this year. Make sure if you liked this video you hit that thumbs up button and go over and subscribe to our channel. And check out our other how-to and DIY videos. Thanks for watching!