when to fertilize new grass

When to Fertilize New Grass For The Best Possible Results

Without fertilizer, you will find that a new lawn doesn’t thrive. While grass isn’t the hardest thing in the world to grow, you will need to apply some care and attention during the process. Using a good quality fertilizer at the right time and in the correct ratio can make all the difference. 

You might think that there’s really no point in exerting the extra effort it takes to fertilize your lawn, but you’d be wrong. It’s super important to perform fertilizing on new grass if you want it to be as lush and green as possible.

Fertilizer is a source of nutrients for the grass. Sometimes nutrients come from natural sources such as organic matter within the soil. However, in many places, there simply isn’t enough of this to help a new lawn thrive.

When the lawn doesn’t have these nutrients, it will suffer. You’ll have issues with weeds, pests and the lawn will be much more prone to diseases. What’s more, you may even find that the lawn becomes sparse and patchy. Not something that anyone wants for their garden!

The answer? Use fertilizer for starting grass. These products contain all of the most essential nutrients your lawn needs so you won’t need to problem solve down the line. That said, you need to be mindful about the type of fertilizer, how much you’re using and when you apply it.e

How to Choose the Best Fertilizer for New Grass

When it comes to taking care of your lawn, you need to compare its need to that of a human. When we’re younger, we have different nutritional needs which change as we get older. The same can be said for grass.

There are different types of lawn fertilizer and many people make the mistake of using regular fertilizer when they should be using starter fertilizer. These are two different products designed to offer different levels of nutrients depending on where the grass is in its life cycle.

While regular fertilizer is great for established plants. Its 1-2-1 ratio of nitrogen, potassium and phosphorus isn’t suitable for new grass. When lawns are freshly seeded, they have a greater need for phosphorus which encourages germination. Moreover, the lawn also needs a quicker release of nitrogen for the same reason. Starter fertilizers contain both of these things.

My Recommended Starter Fertilizer for New Grass

If you’re looking for a high-quality starter fertilizer that is ideal for new grass, Scotts Turf Builder Starter Fertilizer is my favorite fertilizer to use when seeding a new lawn. This organic fertilizer contains all three primary nutrients needed for healthy growth, and it has been specifically formulated to ensure optimal results with new lawns. Whether you’re seeding your lawn or growing sod, Scotts Turf Builder Spray is also a good choice to help get your new grass off to a strong start.

Understanding the Nutrients in Lawn Fertilizer

When it comes to buying lawn fertilizer, it’s really important to understand what’s inside the product. Going by what we know now, there are certain nutrients that are hugely beneficial to new grass so it’s important to choose a fertilizer that’s going to meet these needs.

Generally speaking, you’ll notice that the same three ingredients appear in almost every fertilizer. However, each product has those ingredients in varying ratios. You’ll find details of the ratios on the packaging so you know exactly what you’re buying.

It’s also a good idea to learn some fertilizer jargon; but don’t worry, it’s pretty simple. On the packaging, you will find numbers which represent the levels of nitrogen, phosphorus and potassium. These are called NPK ratios. Regardless of the brand you are buying, these numbers will always appear in the same order nitrogen – phosphorus – potassium. So there’ll never be any confusion!

Before choosing your fertilizer, it’s a good idea to test the toil to determine which is the best product for your lawn. Different soils have different pH levels and varying amounts of nutrients. You don’t want to overload your soil with phosphorus if there are already very high natural levels.

What These 3 Key Nutrients do to Support New Grass

When fertilizing new grass, you’re going to need something that’s higher in nitrogen and phosphorus. Moreover, a quick release fertilizer is going to perform much better. By adding quick release nitrogen, the grass seeds are more easily able to absorb other nutrients, particularly potassium. But let’s take a look at why these three nutrients are so important.

  • Nitrogen encourages better above ground growth so your lawn will appear much thicker and greener. 
  • Phosphorus ensures that the grass establishes strong and healthy roots.
  • Potassium helps to strengthen the grass and make it more resistant to diseases.

Starter Fertilizer Ratios for New Grass Seed

We have already touched upon the ratios that you’ll see on packaging for lawn fertilizer. But since there are so many options, it can feel confusing when finding a fertilizer for starting grass. Typically speaking, you’ll want to find something that has a ratio that is exactly or as close as possible to 21 – 22 – 4.

Notice that the potassium level is nowhere near as high as the other nutrients; this is quite normal. Since there is a lot of potash within the soil, there’s no need to starter fertilizers to contain as much. Make sure that whatever fertilizer you choose, it is a quick release product as this will get to your grass seeds as quickly as possible. The result? Your lawn will establish much faster and be healthier.

broadcast spreader

When to Fertilize New Grass

Once you have seeded your new lawn, you’re probably keen to feed it right away in the belief that this will speed up the growth and establish things much more quickly. While this might make sense, the reality is far different.

You will need to wait at least four weeks before fertilizing new grass.

In some situations, you may even need to wait as long as eight weeks.  While it’s tempting to do it sooner, this could mean that the nutrients are properly absorbed. As a result of this, there’s a chance of run off which essentially means that the product will contaminate water supplies or local wildlife. 

A lot of people don’t realize that fertilizing too soon or too much can actually take nutrients out of the soil which means that it won’t be able to provide everything your grass needs over the course of time.

Fertilizing in Summer

If you’re keen to fertilize your new lawn at the optimal time then early summer is ideal, especially for new lawns or those in need of some serious TLC.

Once you have applied your initial starter fertilizer, you can then give your lawn a boost using a slow release product. You’ll need to leave at least 45 to 60 days between applications and the slow release nitrogen will boost the lawn without making it grow out of control.

Fertilizing in Fall

A lot of people swear by fertilizing in fall and there are some arguments for this. For starters, doing this will encourage a denser lawn as well as preventing weed build up over winter. You’ll also notice that the color of the lawn remains much brighter throughout the season than it would if you didn’t fertilize it first.

When spring rolls around, the lawn will be healthier and therefore much more easily able to recover from the winter. Just make sure that you use something that’s not too high in nitrogen and that you apply the fertilizer before it gets too cold and frosty.

Fertilizing in Spring

If you’re going to fertilize in spring, then you’ll want to do this between March and April. Of course, this will vary according to your location but if you look at your lawn, you’ll be able to see when it needs some attention.

Before you fertilize in the spring, your lawn should look green and should be growing at a rate that you have to mow it a couple of times before adding any products. Also be sure to remove any weeds as these can hinder the process.

How Often to Apply Starter Fertilizer on New Grass

You have added starter fertilizer when installing your grass so you’re probably wondering if it needs a top up. The truth is that it doesn’t. The clue is in the name: starter fertilizer is designed to be used at the start of the lawn growing process. Using it after this can actually do more harm than good.

Once your lawn becomes established, you’ll need to switch its food to something more age appropriate. This is where regular fertilizer becomes your new best friend.

How to Fertilize New Grass Seed

If you have recently seeded your lawn, it is important to fertilize it in order to help the new grass plants grow healthy and strong. Fertilizing your new grass seed can be done in one of two ways: by broadcasting the fertilizer over the entire lawn by using either a drop spreader or fertilizer spreader, or by applying it directly to the areas where the new grass seeds have been planted.

Some people are under the impression that fertilizing on new grass is just an extra step that’s going to be a lot of work. But that’s not the case. You’ll need to start by weeding the area that the lawn will be installed upon and make sure that the soil is nice and loose. If it’s not, then rake it gently.

Now comes the fertilizer which you can either add to the soil before planting the grass seed or at the same time as this. Once you have spread the seeds, make sure to cover them over with a light layer of soil; using a rake is the easiest way to do this. You can water the seeds but be mindful not to disturb the soil over the top of them.

10 Steps for Fertilizing New Grass

Here is our quick guide to fertilizing grass the easy way. You’ll need to do a bit of prep but the result will be a gorgeous green and healthy lawn. 

    1. Start by dethatching and aerating the lawn if this is necessary. If it isn’t then you can simply use your rake to loosen the soil and remove any old grass or debris
    2. Apply your chosen starter fertilizer over the entire area that you will spread the grass seed.
    3. Take your grass seed and spread this generously around the soil.
    4. Take a leaf rake and use this to work the seed into the soil.
    5. Use compost over the top of the seeds; applying between ¼ inch and ½ inch should be more than sufficient. 
    6. Water the grass seeds so that the compost is kept moist.
    7. When the seedlings become established, you can cut down how often you water them as this will encourage the roots to grow more deeply. 
    8. Wait until the grass is around 3 inches in height before mowing and remove no more than ¾ inch. Avoid mulching the clippings. 
    9. Wait for the grass to grow back to 3 inches and mow again, taking off no more than 1 inch. 
    10. After six to eight weeks, you can apply a fertilizer that has a higher nitrogen content, although this step is optional.


Having a beautiful lush lawn is the dream of most homeowners but without the proper care, your lawn will not flourish. Using a good starter fertilizer will  promote healthy growth and offer protection to your lawn.


Yes, you can put fertilizer on new grass seed, but you should consult the directions on the package carefully to make sure you are using the correct dosage. Over-fertilizing can damage your lawn, while under-fertilizing will not provide it with the nutrients it needs to thrive. If you're unsure of how much fertilizer to apply, it's best to err on the side of caution and apply a lower dose.

No, fertilizer will not kill new grass. However, over-fertilizing can damage your lawn, while under-fertilizing will not provide it with the nutrients it needs to thrive. If you're unsure of how much fertilizer to apply, it's best to err on the side of caution and apply a lower dose.

It is important to water your lawn well after fertilizing in order to help the fertilizer penetrate the soil and to prevent the fertilizer from washing away. How long you need to water your lawn will depend on how much rain or watering your lawn receives naturally. As a general rule, you should continue to water your lawn until it begins to look wetter than usual.

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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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