Last Updated on April 28, 2021

Planting Grass Seed Over Existing Weeds

You may have a few weeds. It happens to everyone. Will grass seed still be able to thrive and grow amidst a few weeds?

Surprisingly, planting more grass is helpful to fend off the weeds! If those annoying weeds have less area to grow, they won’t spring up as fast. You asked, and I answered. Find out everything you need to know about weeds and grass seed!

Do I need to remove weeds before overseeding?

This depends on the time of year. Weeds tend to really thrive and spread during the middle of summer. The middle of summer is also the worst time to plant grass seed.

Weeds will dominate any thin areas of lawns! Try to catch thin areas of the lawn in the spring when the weeds are just starting to take over. This is a great time to apply new grass seed and choke out the weeds!

The weeds will win the battle for your yard in the summer. Use the time during the hot months to apply a weed killer or weed and feed. Get the weeds under control before it is time to plant seed in the fall.

Fall is a great time to overseed! The weeds should be dying down at this point. Check your local weather forecast for frost warnings. It is best to plant grass seed at least 45 days before the first frost. This will allow the new seed to take root before it goes dormant.

Can I plant grass seed over weeds?

Grass seed can be planted in a weedy lawn. However, if the weeds are very thick, you will get better results if you deal with the weeds first. If there are just a few weeds, pull the largest ones, then apply the grass seed.

How can I prevent weeds when planting grass?

We’ve all heard the saying, “An ounce of prevention is worth a pound of cure!” This is true of weeds, as well. There are several easy ways to prevent weeds when planting grass.

Buy quality grass seed

Look for a reputable brand of grass seed. It should list “weed seeds 0%” and “other crop seeds 0%”.

Spread mulch

Many people will spread hay over new grass seed to protect it as it starts to grow. Often hay will contain weed seeds or hay seeds. Use a paper pellet mulch instead to keep your new grass weed free, protect it, and lock in moisture!

Stay alert for weeds

If you do see any weeds pop up in the grass seed area, pull them right away! Don’t use a weed killer quite yet. Your new grass can’t handle an herbicide at this stage.

Water your soil well

Healthy grass is a good weed preventer! Keep your new grass fed and watered as it grows. If it comes in thick and healthy, there won’t be any room for weeds!

Eventually use weed and feed

Once your new grass is established and mowed two times, it is time for weed and feed! Follow the instructions on the package for the best results.

Is there a grass seed that kills weeds?

While certain types of grass choke out weeds once they are established, grass seed on its own will not kill weeds. Zoysia is a popular choice of grass for weed control. It forms a thick turf that won’t allow weeds to grow.

Will overseeding choke out or Kill weeds?

Thick, healthy grass is a great weed deterrent! Unfortunately, new grass seed is no match for established weeds. Weeds are at their peak during the middle of the summer. If you plant grass seed in the spring, the weeds will have a lot less room to grow and take over during the summer.

Or, apply grass seed in the fall before the first frost. The weeds should be dying off as the evenings get cooler.

Should I apply weed and feed or seed first?

Apply the fertilizer first. Weed and feed contains an herbicide that will kill off existing weeds in about two weeks. This will give your new grass more room to grow and thrive!

Picking Weeds From Lawn

How do I grow grass in a weedy yard?

Step-by-step instructions for overseeding a weedy yard

  1. Water thoroughly. Start before you intend to plant grass seed. Make sure the ground is thoroughly soaked every time you water.
  2. Deal with weeds. Start by pulling or digging any very large weeds. Apply a weed and feed or herbicide to kill off the remaining weeds.
  3. Mow it short. Trim your grass to about 1.5 inches tall. Make sure to bag up all clippings. You want to make sure the new grass has as much access to sunshine and soil nutrients as possible.
  4. Dethatch/Aerate. This step is optional, but it will help the new grass and existing grass. Dethatching is the process where the thatch layer is removed from the grass. This is usually done with a rake or power rake. Aeration punches holes in the dirt. Both of these jobs can be done by a lawn care professional, or you can rent the equipment and do it yourself.
  5. Apply fertilizer. Find a fertilizer specifically for new grass. Follow the package instructions for the best results. If you are applying seed to a completely bare patch of ground, a layer of compost may help the new grass get started.
  6. Plant the seed. The general rule is 15-20 seeds per square inch, or several pounds of seed per 1,000 square feet of lawn if you are overseeding the entire lawn.
  7. Water again. Lightly water the newly seeded area twice a day for the first week, then daily for the next few weeks.

Wait until the grass is 3-4 inches tall before mowing for the first time. Avoid weed killers until the grass is established, as well.

Final Thoughts

Weeds are frustrating! With a bit of patience and work, you can take back your yard with new, healthy grass!


Author: Matt Hagens

Hi, I’m Matt the owner of Obsessed Lawn. I love to be outside working on my lawn, planning my next project. I created this website to help people like you find the best products for yard care and great advice. Learn more about me and find me on Facebook.