When to Fertilize New Grass for AMAZING Results!

There are many steps that lead to a lush, healthy lawn; and using a good-quality fertilizer can be one of them.

But knowing what to use, and when to use it, can be the tricky part.

And this is particularly true when establishing new grass.

Should you wait for a particular month? Does temperature make a difference? How much is too much?

Whether you’re overseeding, repairing bare spots, or starting a brand-new lawn, read on to discover when to fertilize new grass for the best possible results.


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New Lawn Fertilizer Guide – The Short Version

To keep things simple and to the point, here’s a brief summary of this article for anyone in a hurry:

If you decide to lay down fertilizer at all, it’s important you adhere to the instructions on the label of the particular product you’re using.

new lawn growing

Some fertilizers can be applied immediately at seeding, others after a couple of weeks, and others not until the grass has become established – maybe six to eight weeks later.

You might also like to add a second application when the grass is actively growing, around the time of the first mow.

Either way, stick to the application guide, and you won’t go far wrong. Keep reading for a more detailed look at fertilizing new grass seed.

Sod vs Seeds

The term “New Grass” can have different connotations.

And if you’re looking to revitalize an area of your property, when it comes to lawns, you have two options.

You can seed, or you can sod.

Seeding is cost-effective, but it takes time and can be a long-term, ongoing process.

Laying down sod is faster by contrast, but is also much more expensive.

And you should use a different type of fertilizer and/or a different schedule depending on which method you choose.

bag of lawn seed on grass

In this article, we’re using the term “New Grass” to refer to seed. But if you are using sod, you can add fertilizer as soon as it’s been installed.

Can You Fertilize New Grass?

It’s a valid question – should you even be applying fertilizer to the grass seed you’ve just laid down? How soon is too soon?

New grass can be fragile when it’s just starting out, and there’s a danger you can smother it with too much attention, such as overwatering or adding too much of a starter product/fertilizer.

You certainly don’t want to be dumping fertilizer in the belief that more is more.

In short, the answer is ‘yes,’ you can apply fertilizer to new grass – but you need to get your timing and quantities right to stand the best chance of success.

You also need to understand the types of fertilizer available – so you can choose the right one for your fledgling lawn.

Weed and feed products might look attractive, for example, but they’re not suitable for new seed, and can actually inhibit new growth.

lawn fertilizer in bag

Read on to find out more.

Types of Fertilizer

There are several types of fertilizers available on the market, and you might be scratching your head at which one to choose.

It can be very confusing – even for professionals!

Synthetic vs organic, liquid vs granular, weed and feed products vs dedicated fertilizers.

Not to mention season-specific options and/or starter fertilizers designed to be applied at a certain time of year or specifically to new seeds.

For more information, head on over to this link to explore the different types of fertilizer available. It will also explain those confusing NPK numbers (Nitrogen, Phosphorus, Potassium).

However, when it comes to starting a new lawn, you should be looking for a fertilizer that has a higher nitrogen and phosphorus content.

Having said that, a 10-10-10 fertilizer is a milder, more balanced option that can work wonders for new grass seed.

And this article on liquid vs granular fertilizer will help you decide between the two for most general garden uses.

But for a new lawn, I would suggest a granular product, as they offer a slow-release formula that is better for the grass over time – and doesn’t require as many applications as a more fast-acting liquid.

granual lawn fertilizer

How Soon Can You Fertilize New Grass?

It appears there’s a lot of misinformation on the internet – but what else is new?

And there’s no exception when it comes to the timing of seeding and fertilizing.

Some lawn-care professionals advocate for laying down fertilizer before you seed.

Others will swear by fertilizing immediately after seeding.

And some will tell you to wait until the grass has had a chance to germinate – around six to eight weeks after sowing.

So, which is the right method?

It might just come down to personal preference/whatever works for you/trial and error.

In my experience, for example, I’ve had the best results in my lawn by sticking to the following regimen:

  • Seed the area.
  • Wait a day or two, then add a lawn-starter fertilizer.
  • Six weeks later – lay down a light second application of lawn-starter, to the actively growing grass.

But so long as you’re not smothering the new seed, and adding the incorrect product (such as weed and feeds or improper NPK levels for your soil), then you can feel free to experiment to get the best results.

It also depends on the product you’re using. Some fertilizers will advise you to lay it down immediately before seeding, some after, some maybe two weeks later, others later still.

And some products might say it doesn’t really matter at all – and it’s up to you to decide when is the best moment to throw it on!

When in doubt, always follow the instructions of the particular product you’re using. Providing, of course, you’re using a suitable product in the first place.

Remember – you don’t actually need to use fertilizer at all – and we have more information about that in the FAQ section at the end of this article.

person fertilizing lawn with liquid fertilizer

How Often Do You Fertilize New Grass?

You might think that adding more fertilizer to an area of new grass is going to help it establish and grow faster.

This isn’t the case.

New grass should be fertilized between two-to-four times a year. That’s if you decide to fertilize it at all!

Once, when you lay the seed down (either in the spring or the fall – or both).

And a second application six-to-eight weeks later (again, either in the spring, fall, or both).

Math isn’t my strong suit, but I believe that adds up to an absolute maximum of four times in one year.

It’s very important you don’t over-fertilize – particularly when it comes to new grass seed.

You might think that giving it more food is going to be beneficial, but it will actually have a negative effect on plant life, and you could end up “burning” your lawn.

This article at this link provides general tips and advice on when to fertilize your garden, regardless of if it’s a new patch of fresh vegetables or a tired old lawn you want to revitalize.

Steps for Starting a New Lawn – A Brief Guide

Below, I’ve included a brief summary of the process to starting a new lawn in a step-by-step, at-a-glance guide.

We don’t go into too much detail here, as it’s more to give you a general idea of when you should fertilize a new grass seed.

There is a more in-depth, month-by-month lawn care calendar at that link, plus many other lawn care articles on Yardthyme for addressing and treating specific needs.

Before you begin, however, you should make sure you have at least some of these essential lawn care tools in your shed.

You might be able to get by without them, but it’s going to make life much easier if you have them to hand.

Follow these steps for the best chance to achieve a healthy new lawn:

  • Weed control – begin by removing/killing any weeds and unwanted plants in the area. Remember – you’re going to be planting new seeds, so stay away from harsh herbicides.
  • Dethatching – remove dead plant life and material. Follow this ultimate dethatching guide to learn how.
  • Aeration – if your soil is too compact, it needs a little help to allow water and nutrients to flow, particularly for new grass. Aeration can also help new seeds become established in the soil.
  • Seeding – use a broadcast seeder (or a tow-behind spreader) to distribute new seed at the recommended rate.
  • Watering – Not too much, not too little. This guide on how to properly water your lawn should tell you everything you need to know. For new grass, half an inch, twice a day is a rough guide.
  • Fertilizing – if you’re using a starter fertilizer, apply it a couple of days after you’ve seeded. For anything else, wait six to eight weeks to give the grass a chance to germinate and develop.
  • Mowing – New grass should be at least three inches high before the first mow. Make sure your mower is in tip-top condition while it waits.
  • Second fertilizer application – depending on the product you’re using, you might want to add a second boost of fertilizer when the grass has taken root and is actively growing.

Of course, there’s much more to the process, and it might take several seasons before you achieve the lawn of your dreams.

But that will give you a very basic idea of a new lawn-care schedule, so you understand where fertilizing comes into play.

Also, it’s worth noting if fertilizer can kill weeds – so you can save time and money when establishing your new lawn.

That link will tell you more, but I would avoid using two-in-one products when sowing seed, as even mild formulas might inhibit germination, and new grass needs all the help it can get.

The video below from the ever-popular lawn-care expert Ryan Knorr will tell you more when it comes to mowing, watering, and – of course – fertilizing new lawns.


Does fertilizer go bad?

It can be infuriating when you reach for a particular product to find out it’s well past its use-by-date. I once found a tin of beef stew in my grandma’s cupboard from 1956!

And as fertilizer is regarded as “plant food,” perhaps it follows similar rules?

This article answers the question – does fertilizer go bad? So you can better understand its shelf life.

And while we’re on this subject, it might be also prudent to know if grass seed goes bad. Follow that link to find out if you can use that bag you bought six years ago.

Spoiler: you can’t.

Do I need to fertilize new grass?

No. Contrary to popular belief, you don’t actually need to use fertilizer at all. If you already have good, healthy soil with a balance of nutrients, then adding fertilizer is unnecessary.

How do you know if your soil is healthy? Use a soil testing kit, of course!

Fertilizer run-off is a real problem and has seen a negative environmental impact in many states. You should avoid using fertilizers if you can’t control run-off in your yard.

An excellent alternative is to apply a topdressing of quality compost. Done correctly, new grass seed will have everything it needs to grow into a lush, healthy, green lawn.

And if you don’t want to buy compost – then making your own is going to save you loads of money. Pick up a kitchen compost bin and a compost tumbler to get started making the all-natural black gold!

It’s perfect for organic gardening, too!

Does Fertilizer kill worms?

Worms and other helpful insects can be very beneficial in our yards and gardens – particularly when starting new plant life.

As such, for nature-conscious gardeners (which we all should be), we need to be aware if fertilizer can harm or kill such organisms. Follow that link to find out.


It’s important to understand when to fertilize new grass, so you don’t end up damaging the seeds, and you give it the best possible chance to germinate, and grow into the field of dreams.

And as there’s a lot of conflicting information out there, some trial and error might be involved before you see success with your lawn.

Feel free to share your lawn starter tips with the community. What worked for you? What would you have done differently? Are there any quality products we should be aware of?

Stay safe out there, and happy gardening!

Andy Gibson

My name's Gibson. Andy Gibson. I like to think of myself as the Bond of the backyard, that is if yard work ever became sexy. I write about everything about indoor and outdoor gardening and the dread-it-but-still-need-to-do-it chores around the yard, like cleaning out the gutter guards.

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