What weed and feed can i use with new seed

When to Fertilize New Grass for Best Results

Growing grass generally doesn’t take an agonizing amount of effort. But cultivating a new lawn requires a certain level of diligence to give grass seed the best chance to germinate and thrive. It is also important for roots to grow deep into the soil in order to form a well-established lawn. In this article I’ll explain when to fertilize new grass so that you can enjoy the best results.

The key benefit of a well-established lawn is that it will be hardy and more resistant to inclement conditions.

Fertilizer provides grass seed or newly germinated grass with concentrated nutrients. While you could introduce fertilizer at any time (or not at all), fertilizing grass at just the right times in the growth cycle can put your grass into “hulk mode” – if you will. The nutrients available in fertilizers also come in varying percentages that can be more beneficial for different stages of growth. Choosing a fertilizer that is too highly concentrated can actually burn your lawn!

Why Should I Fertilize New Grass?

Fertilizers contain essential nutrients that can improve overall soil health in your area. The main nutrients in fertilizer are potassium (K), nitrogen (N), and phosphorus (P). Healthy soil is more resistant to weeds, pests, fungus, erosion, runoff, and patchy grass. Soil that lacks the essential nutrients can be difficult growing medium.

That being said, too much can lead to burning and using the wrong fertilizer can have far-reaching effects on the soil in your area.

When the ground is saturated with the nutrients found in fertilizer, it can end up leaking through to the water table and lead to runoff. Runoff of fertilizer chemicals has been found to be responsible for toxic algae blooms in local ponds and lakes that are harmful to people and pets. For this reason, fertilizers are often highly regulated and often only certain amounts can be purchased at a time.

How to Choose the Best Fertilizer for New Grass

There are two main types of fertilizer to start with: regular (or slow-release) fertilizer and starter (or quick release) fertilizer. Consider the dietary needs of humans in different age groups: the needs of a baby are far different from an adult.

“Weed and Feed” fertilizers contain herbicides such as corn gluten to prevent weeds from germinating. This is an important fertilizer to take note of and avoid when planting new grass seed because most of these will also prevent your grass seed from germinating!

My Recommended Starter Fertilizer for New Grass

Crabgrass is everywhere in my area, so my favorite fertilizer to use when seeding a new section of lawn is Scott’s Turf Builder Starter Fertilizer + Crabgrass Preventer.

Unlike many other weed and feed products, this fertilizer does not harm new grass as it germinates, but it does (at least in my experience) successfully block crabgrass and other common weeds for 4-6 weeks to give your new grass time to establish itself. One bag goes a long way too.

Understanding The Nutrients in Lawn Fertilizer

There are three main nutrients in lawn fertilizer. Every fertilizer has a different ratio of these nutrients, and these ratios are on fertilizer packaging as a set of three numbers separated by dashes.

The sequence of numbers indicates the amount of nitrogen, phosphorus, and potassium, respectively and are thus known as NPK ratios.

If you see three numbers on a bag of lawn fertilizer, those numbers will be listed in this order:

Nitrogen – Phosphorus – Potassium

A soil test can help you determine what type of fertilizer will best support your lawn’s health, just make sure you buy a kit that goes beyond simple PH levels and measures these three nutrient levels like this one.

What These 3 Key Nutrients Do to Support New Grass
  • Nitrogen is important for the leaf growth you see above ground and helps grass look greener.
  • Phosphorus is responsible for promoting root growth below the ground and is important for getting a lawn established.
  • Potassium prevents disease and makes the grass more resilient.

New grass seeds need a starter fertilizer that has a higher level of phosphorus and nitrogen that is quick-release, thus readily available for the seeds to absorb.

Quick-release nitrogen also helps seeds absorb more potassium. Some areas actually restrict phosphorus usage exclusively to those starting new lawns.

Fertilizer Ratios for Established Lawns

An established lawn thrives best with a fertilizer that is high in nitrogen. Mature lawns don’t really need much potassium or phosphorus, so you will look for a ratio with a large first number and smaller second and third number. For example, a 30-0-0 or a 27-3-3 ratio would be most appropriate for an established lawn that you want to green up and look beautiful.

Starter Fertilizer Ratios for New Grass Seed

A good starter fertilizer for new lawns should be closer to a 21 – 22 – 4 ratio of nitrogen, phosphorus, and potassium, and those nutrients should be quick-release so they’re accessible to your seedlings right away to help your new lawn establish itself as quickly as possible.

Potash commonly found in soil is a source of potassium, so it is common for the levels of potassium in fertilizer to be very low.

When to Fertilize New Grass

It is important to make sure that your soil has the appropriate nutrients for new grass seed prior to dispersing the seed itself.

So, after preparing your soil for seed or sod, the last step before planting is to fertilize the soil with a starter fertilizer. This can be done before you lay seed or sod, or at the same time.

After you apply starter fertilizer, don’t reapply it. The ratios of nutrients can actually be harmful and burn established grass. I recommend using a traditional, nitrogen-rich organic fertilizer 6-8 weeks after planting new grass.

While you may be eager to fertilize again to encourage growth, fertilizing too often is harmful. It can burn your grass, leach into the water table, and more. It’s important to wait a minimum of four to six weeks before another application of fertilizer, and I recommend 6-8 weeks.

My Process for Seeding a New Lawn

  1. Dethatch and Aerate the lawn if needed.
  2. If lawn does not need to be dethatched, use an iron rake to loosen the soil and remove dead grass.
  3. Remove any dead grass from the area you will be seeding.
  4. Apply starter fertilizer evenly across the area you will be seeding.
  5. Apply a generous amount of grass seed that is appropriate for your area and the growing conditions of your lot.
  6. Use the back of a leaf rake to gently work the seed into contact with the loosened soil
  7. Apply 1/4″ – 1/2″ of compost loosely over the grass seed to retain moisture and provide nutrients to the new grass seedlings
  8. Water to keep compost and seedlings moist until well established.
  9. After grass seedlings are established, water less frequently and more deeply to promote root growth.
  10. Mow once grass seedlings are about 3″ tall, removing 1/2″ – 3/4″ of grass blades with a sharp mower blade. Bag these clippings and remove.
  11. Mow again once grass gets to 3″ again, removing no more than 1″.
  12. Apply nitrogen-rich organic fertilizer 6-8 weeks after seeding (optional).
Should You Fertilize Again in the Fall?

An application of a fertilizer that has a modest amount of slow-release nitrogen in the fall can help to bolster your grass before the coming winter. It’s important to make sure that this is done well before the first frost, so no later than November 1st for southern states and an even earlier cutoff for northern states.

Fertilizing with nitrogen before snow can create snow mold and kill your lawn which landscaper Roger Cooke discusses in the video below:

When spring rolls around again, if you already have an established lawn, then the best time to fertilize will be when grass has greened up and you’ve been able to mow a couple of times. Do this about 6 weeks after overseeding. Use regular fertilizer that has a higher ratio of nitrogen.

In late spring and early summer, if your lawn has been a little bit neglected and needs a boost then you can apply a slow-release fertilizer in 45 to 60 day intervals.

My Preferred Slow-Release Organic Lawn Fertilizers

I use either Purely Organic Lawn Food or Milorganite on my lawn – both are effective organic options.

Compost is the best and most natural fertilizer that you can have available at your fingertips, and I try to apply a thin layer of compost to my entire lawn at least once every two years.

Using a dark, rich, and loose compost at least once every three or four years in the early fall can increase the nutrients in your soil naturally.

My town has an organic composting center where residents bring leaf and grass clippings, and residents are able to enjoy free screened compost in whatever quantity they need.

If you don’t have access to this, contact your local nursery – they can probably deliver screened compost to you. If you have a small yard, split a delivery with your neighbors.

How Do I Fertilize New Grass Seed?

Start by weeding the area that you will be planting in, then gently rake the top layer of soil to loosen it.

This is when to fertilize new grass seed. You can apply fertilizer to the soil, or you can do it at the same time as while you spread grass seed.

Spread your grass seed; a popular method is using a broadcast spreader.

Cover the seeds with a very fine layer of soil either by raking in one direction or sprinkling a little layer of soil using the same broadcast spreader. A very light watering is okay, just make sure not to uncover the seeds from their blanket of soil.

Growing, Growing, Gone

In summary, a lawn starter fertilizer high in phosphorus and quick-releasing nitrogen is ideal for starting a lawn from seed.

Regular slow-release fertilizer that is rich in nitrogen is best for planting sod or giving your existing lawn a boost. It is best to apply starter fertilizer just before, or at the same time as planting grass seed. Follow-up at least four to six weeks later with a regular fertilizer.

More frequent application can be harmful to your lawn and the environment, so don’t overdo it.

A final application of fertilizer in the fall before the first frost can also provide a beneficial boost for your grass through the winter and lead to more growth come spring. I like to use a phosphorus-heavy fertilizer in the fall to encourage deep root growth. This way my lawn is ready for an organic nitrogen treatment in the spring to green up beautifully.

Answered: When to Fertilize New Grass

Growing a thick and lush lawn that will be the envy of your neighborhood isn’t as complicated as it may seem.

Most grasses require only a small amount of maintenance to grow quite robust.

Properly timing the application of fertilizer can give you the most “bang for your buck.” It can also give your grass a boost in growth without burning your lawn or leading to harmful runoff.

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by Sarah The Lawn Chick

I’ve learned to love caring for my lawn naturally and enjoying it daily. On this blog I’ll share some of my best tips and tutorials to help you make your lawn the best on the block!

10 thoughts on “ When to Fertilize New Grass for Best Results ”

Hi Sarah,
I overseeded two weeks or more ago and am just now starting to see some of it grow. I didn’t fertilize immediately before or while planting. Is it too late to apply any fertilizer of any sort, starter, etc? For full disclosure of the situation, I had applied a weed and feed probably 5 to 6 weeks before planting seed, not realizing part of my lawn was only weed, which resulted in lots of brown, bare areas! That’s why I overseeded with Kentucky 31 Tall Fescue later. I’ve been watering everyday since planting.

Thank you!
Steve

Great question. The best time to fertilize new grass grown from seed is with a good starter fertilizer high in phosphorous right when you sow the seed, but if you missed that window and your grass has already germinated I’d recommend holding off until your new grass seedlings are about 1.5 inches tall. At that time, apply a good all-around lawn fertilizer that’s high in nitrogen.

Applying starter fertilizer to new grass risks burning your young seedlings, which is why it’s typically best to add those nutrients to the soil at the time of sowing your seed. This way the nutrients are accessible to your new shoots of grass, but have soaked in with your regular watering as you wait for your seed to germinate.

As I say in the article above, anyone who uses starter fertilizer when spreading seed should wait about 6 weeks to fertilize again, but in your circumstance (which is one a lot of people find themselves in), I’d suggest applying a good all-around lawn fertilizer when your new grass seedlings are almost an inch and a half in height. Something organic and slow release is the safest option as you won’t risk burning your new grass with that, even if you over-apply by mistake. If you choose to go with something synthetic, go light with the first application (0.5 – 1 pound of Nitrogen per 1,000 square feet). You can read my recommendations for organic lawn fertilizers right here, and if you’re not sure of the square footage of your yard, here’s a list of some online tools you can use to get accurate measurements of different areas of your lawn.

Hi, I’ve got a new lawn that was planted about 3 weeks ago. I have been watering on a regular basis. It’s coming in nice and thick in spots but other spots it seems like it’s just starting to grow.or even some spots bare. Is there something I can put on it to boost it up. Or leave as is… thanks for any advice

Thanks for the comment. When you’re seeding a new lawn it’s pretty common to get some spots here and there that are thin or bare. This is something you’ll just want to spot-treat with some more seed and peat moss to get those spots to fill in – that’s my best advice. If you’re growing a grass that spreads via rhizomes, the thin areas should take care of themselves over time … but I’d still probably get some of the same seed you used to patch the bare spots and get some grass growing there too.

This happens to everyone when seeding a new lawn – it’s part of the process. Wind, rain, birds, a funny bump with your spreader, or just a heavy hand with the rake when raking in your seed can all cause some sections to get a little less seed than others. Patch ’em now and in 3 more weeks you’ll have a beautiful lawn! Good luck

We have been following our local seed & garden store’s advice on a new lawn- no fertilizer till 3rd mowing., then apply starter fertilizer. So far it looks beautiful. They said to then apply a regular fertilizer after 6 more weeks. As we just read your advice and it differs should we do anything different since the starter fertilizer was applied later? What fertilizer should we switch to?

Thanks for the comment and I’m so glad your new lawn is coming in well. If you’re having good results based on their advice I’d probably recommend you stick with it. 6 Weeks after you applied starter fertilizer sounds right to me.

Personally, I like to go organic/slow-release with my regular lawn fertilizer so I’d follow-up what you’ve done with something along those lines. I like Milorganite, Purely Organic Lawn Food, or Espoma’s organic lawn fertilizer – any of those will work well for you. Follow the application rate on the bag, and if you want to get an accurate square footage size on different areas of your lawn, these tools can help you do that.

We have a new sod laid down by our builder in our new build home at the end of September in Ottawa, Ontario. I am trying to water once every day since it isn’t too warm anymore here. When is it a good time to over-seed or fertilize the new grass using Fall food before Winters and how long should I wait before the grass is established? The temperatures have started to lower a bit already. Thanks.

For cool-season lawns I like to do my final fertilizer application of the year (fall lawn food) in late October or Early November. Since you’re pretty far north I’d say any time between now and the end of the month is fine.

Since it’s brand new sod my guess is you won’t have to overseed right away, so you can probably do that next year – either in the spring or (ideally) in the fall.

Hi Sarah;
I also missed the fertilizer at the time of new seed, and now grass is about 1″ tall, should I apply “Scotts starter fertilizer (since its first time I am planning to grow grass) or just the one you suggested with high nitrogen ?

If your grass is growing well I’d probably hold off and give it a shot in the arm with one of the organic fertilizers I mentioned above in the article. I would apply it after you do the first mow, once your grass is 3″ or taller. Bag those clippings, then feed it with the slow-release fertilizer. At this time of year a fall fertilizer is a good alternative to those I mentioned above (though they’ll work fine as well). Some of the fall lawn fertilizers have some extra phosphorus to help with root development, which may help since you skipped the starter fertilizer with that.

Sometimes a quick-release starter fertilizer after your young grass is already growing can burn it, which is why I recommend applying something else after your seedlings are more established.

What’s First: Feed, Weed or Seed?

This is a big question in early spring: “My lawn needs everything what should I do first, put down seed or kill my weeds? The reason why this question is tricky is because many of the weed controls will harm new grass seedlings.

Weed, Feed or Seed?

Here are your best two options:

Do you have less than 75% good grass with bare spots larger than a few inches in diameter?

Answer: If lots of larger spots, then seed this spring. Be sure to use a special Starter Lawn Food plus Weed Preventer that is compatible with grass seed (the regular crabgrass preventers will keep grass seed from growing). If you do not prevent weeds when you seed, you are likely to be very disappointed as crabgrass and other weeds will germinate and choke out your good grass before it has a chance to take hold. A machine called a slit-seeder will help make sure the grass seed comes in contact with the soil. You just select the Turf Builder Grass Seed blend that is right for your conditions, such as sun, shade, heat-tolerant, etc. If you only have a few bare spots to take care of, consider Scotts EZ Seed. I think this is the best bare spot repair product we have ever sold! Spread the Starter Lawn Food plus Weed Preventer after you put down the seed. Feed your lawn again in one month after seeding with Turf Builder Lawn Food. Once your new grass has been mowed 4 times, you can kill weeds with Ortho Weed B Gon MAX plus Crabgrass Killer OR Roundup For Lawns.

Do you have more than 75% good grass however your lawn is thin and weedy without widespread bare spots?

Answer: If you have more than 75% grass, you may be surprised how your good grass will fill in with four feedings a year at 6 to 8 week intervals. With this option you skip spring seeding (you can always seed in fall if your lawn still needs it). Here is a schedule for the year: Feed your lawn now with Scotts Turf Builder with Halts Crabgrass Preventer. In 6 to 8 weeks after your first feeding, feed again with Scotts Turf Builder Weed and Feed if you have lots of weeds or if you only have a few weeds, your second feeding can be Turf Builder Lawn Food and spot treat your weeds with Ortho Weed B Gon MAX plus Crabgrass Killer OR Roundup For Lawns. Put down Scotts GrubEx sometime in May or June. In 6 to 8 weeks after your second feeding, feed again with Scotts Turf Builder with SummerGuard to control insects. In 6 to 8 weeks after your third feeding, in late summer/early fall, feed with Turf Builder Lawn Food.

If you have questions during the year, the Scotts Help Center folks will be happy to help you.