overseeding lawn with weeds

Overseeding A Lawn With Weeds: Should I Kill Weeds First?

If your lawn is in need of a little TLC because it’s patchy, sparse or just hasn’t been reseeded in a while then it’s time for some maintenance. However, the lawn is a place where weeds will often thrive and getting rid of them can feel like a lot of work. So, you may have been asking yourself should I kill weeds before overseeding?

If you remove weeds at the end of summer then you can overseed in the fall without too many problems. However, if you’re a little late to the party then you’ll need to scalp the lawn and use a rake to get rid of any debris. After this, you can spread your seeds but you should be aware that there may be some remaining weeds which grow alongside the grass. 

The good news is that you’ll be able to use a post emergent herbicide to take care of the problem before it gets out of hand. 

We would never recommend overseeding over the top of weeds as they’ll simply compete for the nutrients in the soil. This means that the grass seeds won’t be as healthy or grow as well as they otherwise might have.

We would recommend killing any weeds within the lawn before you even think about overseeding. Ideally, you would do this around six weeks before applying any grass seed if you’re going to use a post emergent herbicide. This is because weed killer products can affect how well the grass seed germinates so you’ll want to leave enough time before attempting to plant anything. The label on the product will tell you how long to wait.

The best time to sow grass seed is during the fall. This means that, if you’re going to use a weed killer, you should do this at the end of summer. When fall comes around, there should have been enough time for the product to dissipate meaning it won’t affect the seed germination.

You can remove the weeds manually and we will look at how to do this properly later in this guide.

Can I Overseed After Weed And Feed?

A lot of people wonder whether you can put down grass seed after Weed and Feed. Generally speaking, this isn’t the best idea. You see, these types of fertilizers can also cause problems for the grass seeds when it comes to germination. Therefore, it’s a good idea to wait at least six weeks before you apply any grass seed.

That said, the best option is to check out the instructions on the Weed and Feed as this will tell you a more accurate time frame. Waiting the right length of time will ensure a better germination rate and a healthier, denser lawn.

The Best Time To Sow Grass Seed

Most of us understand that planting grass seed in the fall is the best idea. However, that doesn’t mean that you can’t sow your grass seed at other times of the year. The most important thing is to stay aware of what might happen and the risks involved.

For example, you can plant your grass seed at the beginning of spring but you must make sure that the soil is well drained otherwise you won’t get the best results. During the spring, weeds will be competing much more for nutrients within the soil so it’ll be much harder for the grass seed to germinate and thrive. For this reason, it’s important to make sure that you plant the grass seed before the weeds start to germinate.

It’s never really a good idea to try and overseed your lawn in summer. This is because of the hotter conditions which mean you’ll need to pay closer attention to irrigation if you want success. Moreover, summer will see many more broadleaf weeds which will compete, and likely win, against your grass seed.

Can You Overseed On Top Of Weeds?

It is possible to overseed a lawn where there are a lot of weeds and you may see some success. But on the whole, it’s not really the best practice as you won’t be giving your lawn seeds the best chances of germinating and thriving.

Where weeds are present, there is a lot more competition for the moisture and nutrients in the soil. Established weeds will be a lot stronger than grass seeds and even if they germinate, the seedlings won’t stand a chance against the weeds. For this reason, it is better to remove the weeds before overseeding.

That said, if there are just a few large weeds, you should be easily able to pull these by hand before applying your grass seed.

How To Overseed A Weedy Lawn

If you have a weedy lawn, it can feel like a mammoth task to remove the weeds in order to lay your grass seed. But it’s really important that you take the time to do this if you want the most favorable results.

Weeds tend to grow in sparse areas of the lawn. If there are any bare spots then weeds will thrive here. Moreover, the longer you ignore the problem, the worse it will get which is why overseeding is a good idea as it will create a thicker lawn where weeds will struggle to grow.

So, while you might have to dedicate some time to the job, it will actually save you time and money in the long run as you won’t need to keep removing weeds, buying weed killing products and performing all that extra maintenance.

We’ve detailed some easy to follow steps below. You’ll need to make sure you do everything just right for the best results but it’ll be worth it when you see your lush, thick and weed-free lawn!

1. Pull Out The Weeds

One of the first things you’ll need to do is to get rid of any weeds. A weed puller is a great tool and removing weeds by hand is preferable. This is particularly true if the weeds are visible and large. While you can apply herbicides, this will mean having to wait to overseed the lawn so, where you can weed by hand, do so!

If you’ve never pulled weeds by hand before, there’s no need to worry; it’s pretty simple. Here are some easy steps.

  1. Make sure that you thoroughly water the lawn beforehand as this will soften the soil and make it easier to remove the weeds.
  2. You can use your hands or a weed pulling tool if you prefer. 
  3. Once you have collected all of the weeds, dispose of them well out of the way of your garden so that they don’t spread their seeds again.

There may be some instances that you cannot pull the weeds by hand and a weed killer is the only option. If you have to do this, make sure you leave enough time between using the product and applying the grass seed.

pulling out weeds

2. Dethatch The Lawn

If your lawn has a dense layer of thatch, this can make it more difficult for the seeds to make contact with the soil. For this reason, it’s important to use a lawn dethatcher to remove everything and provide the best conditions for your seeds.

A power rake is a great tool for doing this and when you’re done, you can simply collect the loosened thatch and pop it in your composter.

3. Aerate The Lawn

When fall comes around, you’ll normally find that the soil under your lawn is quite compacted. This causes the grass to grow more slowly but provides better growing conditions for the weeds which will really start coming through.

Once you have removed the weeds and dethatched your lawn, you’ll now need to aerate it which will decompact the soil allowing better air and moisture flow. This will ensure that the roots have better access to all the important nutrients they need to thrive. You can easily rent an aerator if you’re sticking to a budget. 

Another good reason to aerate the lawn is that this will improve the seed to soil contact meaning a much higher germination rate.

4. Spread The Grass Seed

One of the easiest and most effective ways to spread your seed is to use a drop spreader. The tool will come with instructions and various settings so you’ll need to follow these for the best results as they’ll change according to the type of grass seed you are using.

It seems to work better when you cross the grass seeds over instead of planting them all in one direction. We would recommend planting half of your seed in one direction and the remaining half in the other.

Once you have applied the grass seeds, it can help to cover them with a layer of straw. You don’t need to apply too much but a thin layer will stop birds and other animals from damaging the seeds.

5. Rake The Seed In

You cannot simply apply your grass seed and walk away. It’s really important to establish good seed to soil contact. The best way to do this is by raking the seeds in because even when using a lawn spreader, the seed won’t have the best soil contact.

All you need to do is lightly rake the seed over the area you want to cover. Doing this will ensure much faster germination but it will also stop any rain or other water from washing the seeds away.

6. Water Overseeded Lawn

The final step is to make sure that your newly seeded lawn is well watered. Again, you don’t need to go over the top with this; a light watering will work well but just make sure that the soil is nice and moist. Using something like a heavy sprinkler isn’t recommended as there’s a good chance it will wash the seeds away, even if you have raked them in.

How Can I Prevent Weeds When Overseeding?

  • Choose good quality grass seed from a well known and reputable brand. The grass seed packaging should say something like weed seeds 0%.
  • Use mulch. As we mentioned earlier something like straw will offer protection to the grass seeds. However, we wouldn’t recommend hay as this can often contain weed seeds which will undo all of your hard work. Paper pellets are an excellent choice as there’s no chance of weed seeds and they offer brilliant protection and keep moisture in.
  • Be vigilant over the course of the next few months and regularly check for weeds. If you see any, manually remove them as soon as possible. Don’t use any chemicals at this point as this will upset the young lawn.
  • Stick to a watering schedule. It isn’t only just after overseeding your lawn that you’ll need to water it. You will need to stay on top of things over the coming weeks and months. The better you keep the soil moist, the better the chances of a dense lawn and fewer weeds.
  • Using products like Weed and Feed can be done once your new lawn is properly established. However, we would recommend waiting until you’ve mowed the grass at least twice before applying.


Having a weed free lawn is a goal for most homeowners. But it’s important to avoid the temptation to overseed a weedy lawn as you aren’t going to get the results you’re looking for. The weeds will compete with the grass seed which in turn won’t be able to thrive.

It’s much better to remove the weeds and treat the area which processes such as dethatching and aerating before applying your grass seed. Afterwards, you’ll need to take good care of the lawn, regularly watering it to ensure thick growth that will choke out weeds.

Further Reading

Andrew Fisher

Andrew Fisher

Andrew is a dedicated father of three who really takes pride in his lawn and garden. You'll find Andrew behind the scenes of almost everything Edge Your Lawn produces. When he's not helping readers find all the information they need, he's in his backyard working on his lawn and garden landscaping. This year he hopes to build an outdoor deck and sort out his veg patches.

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