How Long After Seeding Can You Weed And Feed

A reader is wondering about combining overseeding and feeding a lawn in the autumn. overseed and feed, or feed later. Find out the answer and more … How to Kill Weeds in Newly Seeded Lawn? Not all of us are born with green fingers, and for some of us, it can be challenging to have something as ordinary as grass grow well. Have you ever One look at your local garden center’s fertilizer aisle and you’re inundated with choices. We’ve taken the mystery out of starter fertilizers for you.

Question: Overseeding and feeding a lawn?

I received this question in August 2017 from a reader called Max. He is wondering about combining overseeding and feeding his lawn.

I am a complete beginner with lawn care and am sorting out a neglected lawn.

The lawn was fed in mid July and is going to be fed again 10-12 weeks later as recommended on the feed bag.

I am wanting to do some over seeding and I believe September is the best time to do this. I have read though that you should feed the lawn when you over seed so my question is if i overseed in September should i feed it early at the same time or overseed and just do an autumn feed in October as planned.


Thanks for the question Max.

It seems that have a good lawn care regime and are feeding the lawn regularly. Well done.

Overseeding a lawn should not interfere with a lawn fertilisation programme. You say that you fed the lawn in July and that the feed will last 10-12 weeks. I do not recommend feeding too soon or you risk over feeding your grass.

Therefore overseed your lawn as in September as planned. It is the best time of year to get new grass established. The new grass does not need any additional feed for the first few weeks of it’s life anyway as everything it needs to grow initially its contained within the seed. However, an autumn feed in October will help it to gain nutrients to put down a good root system and stay strong over the winter.

Overseeding and feeding: Things to note

If you are planning on overseeding and feeding a lawn, take note of the following:

  • Do not put down a herbicide soon overseeding your lawn. Most lawn herbicides advise leaving at least 6 weeks before application on new grass. Read the label. Avoid weed and feed mixes. New grass is very vulnerable and a herbicide applied too soon may kill it. If in doubt, just stick to feed only. Any weeds can be dealt with in the spring.
  • Be careful on new grass. If your grass is not ready for mowing, it is probably not ready for feeding. New grass is fragile, so make sure it is strong enough to be stepped on before walking all over it to feed it. If in doubt, just keep off it. The grass will be fine allowing a few more weeks to toughen up.
  • New grass benefits from Phosphorus. Applying fertiliser with some extra ‘P’ will help the new grass establish a good root system and aid cell division.

Follow these tips and you will have a lovely thick lawn for the following spring.

How to Kill Weeds in Newly Seeded Lawn?

Not all of us are born with green fingers, and for some of us, it can be challenging to have something as ordinary as grass grow well. Have you ever started a newly seeded lawn only to be disappointed when it was infested by weeds a few weeks later?

If you have, then this article is for you. Having the perfect lawn doesn’t have to be something that only belongs to your neighbors. By following our tips, the grass can be greener on your side, too.

Unrooting the Issue Before it Begins

When it comes to newly seeded lawns, you’ll make things a lot easier on yourself if you prevent the weeds from infesting and shooting roots in the first place. Knowing what to do when you see the first signs of roots can prevent roots from becoming established in your lawn.

What should you do to prevent weeds from rooting?

1. Your Seed Selection is Key

The seed you choose is essential here because you want to choose seeds that won’t contain any weed seeds. By selecting seeds that are free of any other seeds, you avoid the possible spreading of weed seeds while you are seeding your lawn.

How do you know if seeds are weed seed-free?

It is crucial that you read the packing when you are looking at seeds. Reading the packing will enable you to know what the contents are, and you should look for seeds that are labeled “weed seeds 0%.” Some packaging will describe weed-free seeds as “other crop seeds 0%”.

Another commonly overseen factor is the process where you might cut down weeds by using a weedeater. This could quickly spread the seeds of weeds and thereby risk possible contamination of your newly seeded lawn. A string trimmer is a much safer option when it comes to removing weeds without spreading their seeds.

2. Mulch Matters

It isn’t uncommon for people to use mulch to assist in the spreading of grass seeds. It is not problematic to use mulch, but you need to select the right kind of mulch. It is vital to steer clear from using hay mulch.

People used to use hay mulch years ago, but it has a very high contamination rate when it comes to weed seeds, so you should never use hay mulch.

If you are keen to use mulch, we recommend that you use paper pellets instead. Not only do they protect the new seeds, but they help hold water, and they block weeds from rooting.

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3. Nurture VS Nature

Healthy grass that is flourishing doesn’t leave any space for weeds to creep in. It is true that when your seedlings are barely just sprouting, they can’t do much against the weeds themselves. However, by proper nurturing, they will grow quickly and healthily, and before you know it, there isn’t any space left for weeds to fester.

It is crucial that you follow the correct practices to keep your seedlings healthy. This includes keeping your seedlings watered and fed. You should always avoid cutting them too early or too short. By providing the best possible beginning to your seedings, you make it very challenging for weeds to invade.

4. Watering

One of the most important things you need to do with newly seeded lawn patches is to give enough water. You need to wet the soil down, reaching at least 6 to 8 inches. However, take care not to water too harshly as it can lead to washing new seeds away or creating puddles.

5. Ease up on watering after germination

You can lessen your watering as your newly seeded lawn patch becomes more established, but it depends on the weather. Watering every day after germination can lead to overwatering, resulting in your seed becoming rotten and its root growth inhibited.

How do you know how much water is just right?

If your lawn is covered with new seedlings, you can skip a day of watering, but you must keep an eye on the grass. If there is a color change from bright green to dull green, water your grass.

However, if there isn’t a color change, your grass is ready for the watering schedule. To find an ideal watering schedule for your lawn, you can stretch the time between watering sessions, with your goal being a schedule of once or twice a week or if you are in a scorching and dry area, as needed. Don’t forget to water deeply when you do water, getting the moisture down 6 to 8 inches.

6. Fertilizing and mowing young seedlings

Your seedlings should be at least 4 inches before you mow them. It is better to wait until the soil is dry before mowing. This will help prevent the tearing up of new turf. Also be sure that your mower is set to the correct setting. You don’t want your seedlings to be shorter than 3 inches.

What Should You Do if You Already Have Weeds?

Sometimes no matter how hard you have tried, weeds invade that vulnerable space of newly planted grass. Most gardeners deal with weeds at some point, so it is beneficial to know how to deal with weeds. There are a few strategies that can be implemented. The most important of these are:

1. Watch Your Grass Closely

Special attention should always be paid to newly seeded grass. In addition, you should be on the lookout for infestations of weeds because it is much easier to keep an early weed infestation under control than one that has already been established.

2. Individually remove weeds

The best thing to do when you see weeds shooting up is to remove them individually. This is the most effective way to keep the weed seeds from spreading.

A safe way to remove weeds is to take hold of them at the base and then pull up slowly. Avoid tugging too harshly because you don’t want to remove only part of the weed while leaving the roots firmly in the ground. If the roots or even just parts of the roots remain, the weed will continue growing. So instead, you want to remove the entire weed.

If you are struggling with more extensive roots, it might be helpful to use a hand shovel first. You can use it to dig around the weed, making it easier to remove the entire weed.

What should you do with removed weeds?

You don’t want to give any removed weeds a chance to spread their seeds over your newly seeded lawn. Therefore, you need to dispose of any weeds you have removed. It is also necessary to fill up the holes left by the pulled weeds to prevent new weeds from taking their place.

Can you put the removed weeds into your composter?

It is not a good idea to place the removed weeds in your composter because you could risk spreading weed seeds.

3. Avoid using weed killers too soon.

It might be tempting to apply weed killer the moment you see that first weed pop out. However, if you use weed killer on newly seeded lawn that isn’t mature enough, the grass and weeds may die. It is a much better approach to remove the weeds one by one if there are only a few weeks.

However, if you are dealing with a considerable weed infestation that can’t be removed by hand, it is best to wait until your grass is more mature before applying weed killer. Your newly seeded lawn should have been mowed at least twice before you should use any weed killer.

4. Use a post-emergent weed killer after the second mowing of your lawn.

You can think about using weed killer after giving your lawn enough time to mature, allowing for at least two mowings. If you encounter issues with broadleaf weeds like dandelions, this is the right course of action to take now.

Be sure to examine the label when working with weed killers carefully. It will specify the waiting time between the weed killer application and germination. It is essential to stick to the waiting time to avoid damage to your lawn.

5. Issues with crabgrass

The process for dealing with weeds such as crabgrass differs because they grow annually. Since these weeds die in the winter, it is better to wait for them to die instead of treating your lawn with weed killer. Once they have died and dried up, remove them, and then in spring, apply a pre-emergent weed killer to your lawn. By doing this, you will be preventing them from returning to your lawn.

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Having a beautiful lawn is something every homeowner wants to have. You can have a weed-free lawn in no time if you nurture your newly seeded lawn and keep an eye out for weeds. It is a commitment that requires time and effort, but it will be worth it when you have the perfect lawn that is lush and healthy.

9 FAQs About Applying Starter Fertilizer to Your Lawn

Whether you are planting new grass from scratch or repairing bare spots, figuring out a proper fertilizer to get your lawn off to the best start can be daunting. Here are the answers to 9 FAQs about applying starter fertilizer to your lawn.

One look at your local garden center’s fertilizer aisle and you’re inundated with choices for producing your vibrant lawn. We’ve taken the mystery out of starter fertilizers for you.

Our Top Picks for Starter Fertilizers:

1. What is Starter Fertilizer?

Starter lawn fertilizer is a small quantity of fertilizer nutrients applied near the seed at planting. It helps your grass seedlings and sod roots establish more rapidly in the soil than regular fertilizer, leading to a thick new lawn in a short period.

Starter fertilizers for grass may differ slightly in composition, but they all give the grass seeds and new sod the nutritional boost required for healthy germination and rapid root growth. They will usually contain equal amounts of nitrogen, phosphorus, and potassium. However, some types contain two parts of nitrogen and one part of phosphorus and potassium.

You can choose between slow-release and quick-release formulations, with the latter delivering a quick green-up dose of nitrogen. It can be applied to all-new lawns, or to help bare spots recover from winterkill or other damage.

What is the Difference Between Starter Fertilizer and Regular Fertilizer?

According to David M. Kopec of the University of Arizona Extension, the main difference is the amount of phosphorus in the fertilizer. Starter fertilizers usually contain 20 percent more phosphorus than regular fertilizers.

2. What is a Good Starter Fertilizer for Grass Seed and Sod?

Starter fertilizers for lawns come in different compositions of the primary nutrients nitrogen (N), phosphorus (P-phosphate), and potassium (K-potash), or the three numbers listed on the package (NPK ratio).

The numbers list the percentage of each nutrient contained in the starter fertilizer for grass. For example, an N-P-K ratio of 10-10-10 contains 10 percent each of nitrogen, phosphorus, and potassium.

When it comes to the specific job of each of these primary nutrients in regards to the health of your turf:

  • Nitrogen: Is required for satisfactory growth and green coloration.
  • Phosphorous: Plays an important role in various growth processes including good root development.
  • Potassium: Promotes good disease resistance, tolerance of drought, and winter hardiness in turfgrass.

Some examples of the formulations of common starter fertilizers for lawns are 10-10-10, 20-10-10, and 16-8-8. Penn State Extension notes that analyses of 15-10-10 or 10-6-4 are also acceptable used as starter fertilizers for grass, as they also promote good early growth and grass development.

3. Can you Apply a Starter Fertilizer to Grass Seed and Sod?

“Yes, both seed and sod,” states Peter Landschoot, Ph.D., professor of turfgrass science at Penn State Extension.

Seed: At the seedling stage, “Grasses need greater amounts of nitrogen and phosphorus than mature grass plants because seedlings are producing new tissues rapidly and thus have higher energy and nutrition requirements.” Overseeding a lawn will take more time, but sod will be more expensive.

Sod: “Even though sod is mostly composed of mature turf, many of the roots have been severed during the harvesting operation,” Landschoot says. Some nitrogen and phosphorus (as starter fertilizer) applied to the soil before the sod is laid should help hasten the development of new roots.”

4. Is it Best to Get a Soil Test First to See Phosphorus Levels?

Landschoot notes, “Because soil-test levels of phosphorus don’t change much over short periods, you can collect soil samples and submit them to a test lab to determine phosphorus levels within a year of establishing turf.”

Nearly all extension service offices offer low-cost soil testing services. Check with your local Cooperative Extension Office for details. Soil samples can be collected at any time during the year as long as the soil is not frozen. Ideally, you want to collect soil and submit the sample(s) to a test lab as close to the time of establishment as possible.

Pro Tip: Make sure to leave time to get the test back with the phosphorus and other recommendations. It can take 1-3 days or up to two weeks to get results, depending on the test. You’ll need a few extra days to buy fertilizers and make necessary adjustments to the soil before planting your new lawn.

5. Is There a Standard Amount of Starter Fertilizer I Should Use?

If you didn’t get a soil test to determine how much starter fertilizer to use for your lawn, Landschoot offers these general recommendations:

  • “Starter fertilizers should be applied at 0.5 to 1 lb. nitrogen per 1,000 square feet. Amounts in excess of 1.5 lb. nitrogen per 1,000 square feet can burn the young turf and result in poor establishment.”

Quick-release nitrogen will speed up seedling development.

Pro Tip: Landschoot notes, “Application of a starter fertilizer is not a substitute for the phosphate and potash recommended on your soil test report.”

6. Are There Circumstances Where you Shouldn’t Use a Starter Fertilizer?

  • You should not use starter fertilizer in areas where you cannot control runoff. Nitrogen and phosphorus from indiscriminate use of fertilizers have caused such great environmental concerns that about half the states in the U.S. have imposed regulations on fertilizer use.
  • Don’t use starter fertilizer if your soil test shows it’s not needed. Instead, apply 1-2 inches of organic fertilizer, such as a biosolids fertilizer or manure-based compost, and work into the soil before establishing your new turf. These amendments contain significant amounts of nitrogen and phosphorus to get your new lawn off to a healthy start.
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Pro Tip: It’s common for homeowners to apply lawn fertilizer, depending on where they live, in the spring, but not before the grass greens up.

Once your healthy lawn has been established, fertilize every six to eight weeks. The best time is late spring for warm-season grasses (e.g., centipedegrass, St. Augustinegrass, and Zoysiagrass) and fall for cool-season grasses (e.g., Kentucky bluegrass and tall and fine fescues).

Follow good lawn care maintenance such as aeration and mowing heights to keep your lawn healthy and beautiful.

7. When Should you Apply Starter Fertilizer?

Apply starter fertilizer before seeding or laying sod, or after you plant the new grass seed. You don’t want to apply it directly to newly planted sod or burning can occur.

Note: Wait six to eight weeks before applying another dose of balanced fertilizer to your grass after planting so it doesn’t burn the grass.

When it comes to knowing how much starter fertilizer for the grass, you’ll need a soil test. The three most important nutrients required for good growth and health of your turfgrass are nitrogen, phosphorus, and potassium, which a starter fertilizer contains.

It’s best to till the fertilizer 4 to 6 inches into the soil along with any additional amendments you are adding. You can also spread it over the site immediately after planting your new grass seed.

Pro Tip: When phosphorus and potassium are applied only to the surface of the soil they cannot move down into the soil fast enough and nitrogen can easily be leached out before the grass even Has a chance to uptake its nutrients.

8. Can I Use a Starter Fertilizer for Grass That is Established?

Probably not. Although you can use a starter fertilizer for a lawn that is established, it’s better to use a well-balanced fertilizer designed specifically for grass that is established.

Starter fertilizer might not contain all the required nutrients for continued growth and good health. It won’t hurt the grass but might lack the needed nutrients that a well-balanced fertilizer for continued lawn maintenance contains.

9. How do you Apply Starter Fertilizer?

If you’re planting sod, apply a fertilizer before you put down the sod. If you’re planting seed, apply a fertilizer either before or after planting the seed.

  • If you apply starter fertilizer before planting grass seed or sod:

Pour the required amount into a standard fertilizer spreader and evenly apply the starter fertilizer over the planting site. Once applied, work the product 4 to 6 inches into the soil.

  • If you apply starter fertilizer after you’ve planted grass seed:

Use the fertilizer spreader and apply it over the soil. Then water in the fertilizer.

There are different types of fertilizer applications. You can choose between liquid or granular. Both supply the essential nutrients; however, Michigan State University recommends liquid application.

Granular fertilizers can be inconsistent in spreading and can be “hot,” burning young plants that are nearby. Follow directions on your chosen fertilizer to verify the best application process.

Pro Tip: If you’re overseeding or using sod, avoid weed and feed fertilizers for four weeks or until your third mowing. The herbicides may prevent root development in your new grass seeds.

Wait Time: On average, grass seed takes about 10 to 14 days to germinate, but it can take up to 30 days.

Phosphorus and its Role in a New Lawn

When it comes to explaining phosphorus and its role, Landschoot notes, ”Phosphorus is included in starter fertilizer primarily to enhance root development. Some research shows little influence of phosphorus on turf establishment in soils containing adequate to high levels of soil-test phosphorus; whereas other studies show benefits even when phosphorus levels are adequate.

Generally, developing seedlings growing in compact soils during cold temperatures are thought to benefit more from phosphorus in starter fertilizer.

Nitrogen, Organic Matter, and a New Lawn

If your lawn is not rich in natural organic matter, nitrogen plays an important role. Landschoot notes, “In cases where soils are not amended with compost, nitrogen is almost always needed for rapid establishment.

Our research shows a greater influence of nitrogen compared to phosphorus on the rate of turf establishment, so if you can’t use phosphorus (or you think there is enough phosphorus in the soil), an application of 1 lb. quick-release nitrogen per 1,000 square feet will speed up seedling development.”

Hire a Professional

If you’re a homeowner that isn‘t down to DIY or you’re frustrated with the progress of your garden oasis, you can hire a lawn care professional to get your dream lawn started while you relax.

Main image credit: Jay Crihfield / Adobe Stock

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Joyce Starr

Joyce Starr has been writing on horticultural and landscaping topics for over 15 years. In addition, for the past 20 years she’s owned and operated a landscaping and design business. She shares her experience and passion for all things green through her writing.

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