Using a pre-emergent herbicide within three months of sowing grass seed may kill it.
There are a few exceptions, but it’s best to wait for 3 to 5 months after using a pre-emergent herbicide as a general rule of thumb.
This amount of time will ensure that the herbicide has lost effectiveness, and your expensive grass seed will be able to thrive.
What’s The Best Way To Reseed Your Lawn After Using Pre-Emergent?
Timing is everything with pre-emergents. You have to get it right for them to be most effective against emerging weeds and prevent them from killing your new grass.
An application schedule that keeps these considerations in mind allows for a thick, healthy, weed-free lawn.
Twice A Year Application Of Pre-Emergents Works Best
Apply pre-emergent herbicide early-to-mid autumn and again early in the springtime.
This will target the vast majority of weed seeds they have a chance to sprout.
Know What You Are Dealing With
Even with a solid schedule, some types of weeds will evade your herbicide treatments.
Identify your renegade weeds and use a product that targets them specifically.
Follow Packaging Directions Closely
Remember that the label is the law any time you use herbicides or pesticides and apply products according to instructions.
Pay close attention to the ratios when you mix up concentrates and water.
Understand that pre-emergent herbicides work differently than post-emergent herbicides.
Apply pre-emergent herbicides over the entire area you wish to treat.
A post-emergent herbicide is best used carefully as a targeted spot-on product.
When Should You Reseed After Applying Pre-Emergent Herbicide?
Generally speaking, grass seed needs to be sown about six weeks before the first frost in the autumn.
So apply your pre-emergent herbicide very early in the season.
Or you‘ll need to use a long-lasting product, such as Barricade, in the springtime and then skip the autumn application.
Some brands are formulated to be safe for grass seed immediately after application.
For example, Tenacity Pre-Emergent kills weed seeds in the soil for a month after application but does not kill grass seed.
Use Tenacity immediately before or after sowing grass seed.
As a bonus, this product also works as a post-emergent herbicide.
Follow Best Practices To Sow Grass Seed Successfully
No matter what herbicides you use, prepare the ground well and provide good care to help your grass seed thrive.
You’ll need to rake and possibly even till bare spots.
Add topsoil to hard, dry soil so that your grass seed can set down roots successfully.
If you are using a spreader, follow these tips:
- Try wearing golf shoes to help aerate your lawn and press the seed into the soil as you sow it.
- If you are hand sowing, mix the seed with topsoil before sowing it to help it settle into place.
- Once the seed is in place, water it in thoroughly to help it get a good start.
- Keep the soil well-watered to support healthy root system development.
- Apply fertilizer as needed.
Avoid walking on your newly seeded lawn, and don’t mow for a couple of months.
It may look a bit shabby for a while, but you’ll enjoy your lovely, strong, healthy, weed-free lawn in the long run.