How Long After Using Weed Killer Can I Plant Grass Seed? (Explained)

How long after planting weed killer can I use grass seed header

If you want healthy grass, you need to prevent weeds from competing with food and sustenance. That’s why you need to kill weeds before planting grass. However, you can’t plant seeds immediately.

How Long After Using Weed Killer Can I Plant Grass Seed?

Generally you can safely plant grass seed around three weeks after using weed killer. However, it does depend on the weed killer you are using and you should always check the label and instructions that come with it. There are some weed killers that allow you to plant grass a week after using it and some pre-emergence weed killers where you have to wait for up to four months.

Why Weed Killers Are Important

Weeds are annoying. Even if some of them are actually quite attractive, you should know that they would compete with the grass in terms of nutrients. 

The nutrition that would solely go to the grass will now be split with the weeds, if you have them. 

Not only that

There are some weeds that would take more, leaving the grass with less. When that happens, your grass will look unhealthy–brownish and with unequal growth.

You can always pull out weeds, which is a very taxing job. But even with all that effort, the weeds will just grow back.  

That’s why

You need to kill them with weed killers. 

Person using weed burner

What is a weed killer?

It is a liquid with chemicals meant to kill weeds.

There are different types of weed killers. Some are made for a specific type of weed while others are for all kinds of weeds. 

Is there a best time to kill weeds?


But you have to know that you can use a weed killer when you have a terrible weed problem, and that is any time. 

However, weeds are usually booming during spring or autumn. This means that you can truly maximize weed killing during this time. 


The best time to kill weeds would be before you decide to plant grass seeds. This means that you don’t have a lawn yet but are planning to have one. 

Think about this:

You also need to make sure that it’s not windy when you apply the weed killer. You don’t want parts of the liquid spraying over plants. 

If the chemical compound glyphosate reaches the leaves, it would penetrate the roots leading to the death of the plant or plants. 

You don’t want that, do you?

There are also different types of weed killers depending on where they are situated in your yard. 

For example, some weeds are located in between pavings. For this, you can use a residual weed killer, which is a potent weed killer. 

When you use weed killer, you won’t be able to plant anything on the soil for three to 12 months. 


You cannot use that kind of weed killer for your lawn. For this, you will need a selective weed killer. 

This is the type of weed killer that will not harm plants. 

Tub of grass seed

How Long After Using Weed Killer
Can You Plant Grass Seed?

Actually, the answer would depend on the weed killer you are using. You would have to read the label or ask the experts for the appropriate time. 


It would take about three weeks for you to be able to safely plant grass seed after using weed killers.

Some of these weed killers contain really harsh chemicals that your young seeds may not be able to sustain. 

What happens when you plant very soon?

Chances are the seeds would fail to germinate. 

If you plant soon after using weed killer, it would be like forfeiting your chance to enjoy a healthy and green lawn. 


There are some weed killers that would allow you to safely plant grass seed in just one week

This is just a matter of reading the label of your weed killer. 


We mentioned glyphosate earlier. This is actually quite good for killing weeds and planting grass seed within 24 hours

Here’s what happens: The glyphosate would move from the leaves to the roots, essentially killing the weeds. 

The good thing is

As soon as the chemical is absorbed by the weed, there are no lingering effects. It is no longer dangerous for other plants. 

As such, you can immediately plant grass seeds a day later. But waiting three days might be a better option.

Just to be sure!

Now, if we’re talking about pre-emergence weed killer, then this would take around four months before you can plant grass seed. 

This is because this type of weed killer would make a chemical gap in the soil that would make an environment that would be impossible for a seed to grow. 


This is the residual weed killer we talked about earlier. 

You need this type of weed killer to decay first before you can make the soil a healthy place to sow seeds. 

It’s the best type of weed killer to use before planting grass seeds. But as we said, the waiting period would be between three months and a year. 

We can’t emphasize this enough:

If you really want to know how soon you can plant grass seed after using weed killer, YOU NEED TO READ THE LABEL OF THE WEED KILLER

That’s the best way to determine the necessary length of time. 

House with nice lawn

How to Use Weed Killer

Again, you have to read the instructions in order to know the best way to use the weed killer. Every pack of weed killers has a set of instructions that are actually very easy to follow. 

Now, there are various ways to use the weed killer. Check out the following:


This is the most popular way. Some weed killers already come in a spray bottle anyway. 

Using spray is best for large areas because the process it’s pretty simple: You just need to spray the affected area. 

Watering can

You need to use a different watering can, not the one you will use for actual watering of plants. You don’t want the water to be contaminated with the chemicals of the weed killer. 

Important note:

Don’t walk over wet areas because you might transfer the chemicals to areas you don’t want chemicals to go via your shoes. 

Person using watering can


Weeds are pests! They will not be good for plants, in general. They are also quite annoying when you are trying to grow a beautiful lawn. 

But you can always use a weed killer in order to maintain a beautiful lawn. If you have yet to plant grass seeds, then you need to use a pre-emergence weed killer. However, you would have to wait at least three months before you could plant the grass seeds. 

Read the label of the weed killer to find out the best time to plant grass, or any other plants for that matter.

You Might Also Like

You know what else could get rid of weeds? The weed eaters! Here’s a list of the nine best weed eaters in the market.

Another way to get rid of weeds is by burning them. We’re not talking about lighting the weeds on fire with a match. There is a tool for that aptly called weed burners. Check out the best weed burners in the market. 

There are at least four ways to kill weeds. Read this to know the best ways to kill weeds.

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