How Soon Can You Weed And Feed After Seeding

Crabgrass preventer helps prevent crabgrass from growing but it can wipe out your newly sown grass seed. Learn how Green Giant gets the job done correctly. Can You Fertilize And Overseed At The Same Time? There are two kinds of people when it comes to yards and plants: those who have gardens and those who have lawns. Oddly enough, gardeners and

Can I Seed My Lawn and Use Crabgrass Preventer this Spring?

Many lawns take a beating over the winter and a nice aeration and over-seeding treatment can work wonders to give you a beautiful lawn all summer long. However, crabgrass is also a concern on lawns.

Crabgrass is the most common lawn weed in Pennsylvania and it is primarily controlled with a crabgrass preventer – which prevents the crabgrass seeds from sprouting.

So, will crabgrass preventer keep my new
grass seed from sprouting?

The crabgrass preventer absolutely can wipe out your newly sown grass seed – for this reason, it is very important that the work is done correctly.

Options to Treat Crabgrass Without Harming new Grass Seed

Note: the information below only relates to the crabgrass preventer that we use on our customer’s lawns at Green Giant. Other materials may or may not give the same results.

The options are listed in the order we consider the most preferred to the least desirable.

Option 1:

  • The fertilizer & crabgrass preventer get applied first
  • Allow the materials time to settle into the soil for at least a few days (preferably with some rain)
  • Then perform the aeration and over-seeding

This process has been studied extensively and the results consistently show that the crabgrass preventer has very little, if any, adverse affect on the good grass seed.

Option 2:

  • First, aerate and over-seed the lawn early in the spring, as early as possible (which is usually when the soil is dry enough)
  • Wait until the majority of the grass sprouts are at least 1-2 inches tall
  • Apply the crabgrass preventer

This process should eliminate any risk of the crabgrass preventer harming the grass seed (since the grass has completely emerged from the seed). The down side can be that the process starts later in the season if the aeration & seeding is delayed. This is ok but it might mean more watering as we get into the summer.

Option 3:

  • Skip the crabgrass preventer
  • Aerate & Over-Seed the lawn
  • Treat crabgrass preventer with a post-emergent spray (after the plant is visible in the lawn)

Although crabgrass can be controlled with a “post emergent” material after the plant is growing, it is less effective (especially in hot, dry weather), more expensive and can damage surrounding good grass. Crabgrass preventer is considered to be the most critical component for effective crabgrass control. If possible, we recommend going with option 1 or 2.

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What NOT to do

  • Do not spread seed on the ground, then apply crabgrass preventer. This will be a disappointment because most of the seed will not survive.
  • DO NOT aerate and over-seed then apply crabgrass preventer before the new seed has grown completely out of the seed. This will also lead to a failed seeding effort.

We are always here to help, contact the experts at Green Giant Home & Commercial today for your free quote!

Lawn Care

Green Giant Home & Commercial’s Lawn Care services control weeds, build the thickness and density of your lawn and protect it from being damaged by insects and disease, providing you with a great-looking, healthy lawn. We offer fertilization, weed control, liming, insect control, and aeration and overseeding. Visit our Lawn Care page for more information.

Tree Care

Green Giant performs: Proper Diagnosis and Treatment of Tree & Shrub Problems, Insect & Disease Control (including Spotted Lanternfly), and Nutrient Management via Deep Root Fertilization to keep your plants healthy and thriving. Visit our Tree Care page for more information.

Vegetation Management

Green Giant’s Non-Lawn Weed Control services eliminate unwanted vegetation in a wide variety of locations for both residential and large commercial/municipal properties. Areas include fence lines, around obstacles to reduce weed eating, stone/gravel driveways & parking lots, swales, roadside/curbside vegetation management and more. Find more information, visit our Vegetation Management page.

Pest Control

Our full service pest control division provides both Year-Round Service Programs that cover the vast majority of pests that you will encounter and also One-Time Corrective Services for pests such as bees, ants, termites or mice. For more information, visit our Pest Control page.

Can You Fertilize And Overseed At The Same Time?

There are two kinds of people when it comes to yards and plants: those who have gardens and those who have lawns.

Oddly enough, gardeners and their various plants often have fewer problems than those growing a lawn of just one kind of grass.

The problem with keeping a great lawn goes deeper than a few weeds, literally and metaphorically.

Your lawn’s soil, the thick root layer known as thatch, and the surface grasses are in many ways their separate beasts, and the only way to keep one healthy is to address them all.

Can You Fertilize And Overseed At the Same Time?

Not only is it possible to fertilize and overseed at the same time, but it’s also actually preferable.

Here’s everything you need to know to ensure your lawn has the healthiest seed growth every time.

The Truth About Your Lawn’s Soil

There’s a five-step process for getting the best lawn.

Step 1: Begin by mowing

Step 2: Dethatch

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Step 3: Aerate.

Steps 4 and 5 are where the confusion lies, as these involve fertilizing and seeding your lawn.

Unfortunately, many people forget that steps 4 and 5 go hand-in-hand, and poor seed growth results.

The reason for this issue comes down to the nutritional value of your lawn’s soil.

Grasses aren’t the heaviest feeders out there, but the shallow root systems can’t get to any nutrients deep below the surface.

Instead, your grass seeds rely on fertilizer to germinate properly.

In the five-step process, it’s not uncommon to see a person fertilizing as one of the first three steps instead of one of the final two, which can lead to losing much of the nutrition fertilizer offers.

Check The Thatch Before Seeding

When most people hear the word thatch, they think of old roofs.

But this concept of thatch has a basis in nature, and grasses are notorious for forming a thatch layer at the surface.

Thatch is useful because it can help insulate grassroots from sudden temperature changes and is made up of living and dead organic matter deposited on the mat-like root system.

Unfortunately, thatch can also grow so thick that it prevents seeds, water, and fertilizer from permeating the soil beneath.

It’s important to check the thatch layer before seeding and dethatch, if necessary, to ensure your seeds properly sow.

A thick layer of thatch forms a barrier between the grass and the soil.

For example, if you spread grass seed on a lawn with heavy thatch, the seed will not reach the soil.

Without soil contact, your grass will not sprout and establish itself.

Check the thatch layer in your yard and dethatch if necessary before seeding.

Thick thatch prevents grass seed from reaching the soil where it can root.

Rent a dethatcher or power rake to remove thatch buildup before overseeding.

Thatch soaks up water and fertilizer, robbing soil and grass seed nutrients and moisture.

In addition to preventing your grass seedlings from taking root, thick thatch also acts like a sponge, absorbing water and fertilizer before it can penetrate the soil.

Therefore, fertilizing on thick thatch will be far less effective.

Removing thatch before overseeding helps you deliver more lawn starter fertilizer to your grass seeds.

Always Aerate After Dethatching!

Another essential aspect of lawn care, aerating the soil, is essential if you want the best results from seeding.

It loosens the soil, allowing the seeds to take root, and will also help fertilizers absorb before they can be degraded by sunlight.

Aerating is best performed after dethatching your lawn and before seeding.

Choosing The Right Fertilizer For Seeds

Once your lawn has been mowed, dethatched, and aerated, it’s time to grab your seeds and fertilizer, but what fertilizer should you use?

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Lawn starter fertilizers have a higher degree of phosphorus. While it’s used primarily in flowering plants for producing blooms, young grasses rely more on phosphorus for healthy root growth.

Fertilizers meant for mature lawns contain very little to no phosphorus, which will prevent germinated grass seedlings from establishing a healthy root system.


A great way to fertilize your lawn is to use organic compost.

The catch, however, is that compost contains nitrogen primarily in the form of uric acid, which is photosensitive.

If you cut corners and fail to dethatch and aerate the lawn, your compost will be rendered mostly useless because it can’t absorb into the soil properly.

Instead, aim to use it within a few days after aeration for the best results.

Note that applying compost usually works better when done after overseeding, although it will also be effective if used before.

Avoid Weed And Feed Products

Any product marked as weed and feed is one type of fertilizer that should be avoided at all costs when seeding.

These products contain fertilizer and pre-emergent herbicides designed to kill broadleaf weeds and many other unwanted lawn intruders for up to 3 months.

Unfortunately, while these tend to be formulated to kill specific plants, weed and feed products don’t discriminate when it comes to seeds and will kill your grass seed along with the seeds you don’t want.

To avoid this counterproductive fate, apply weed, and feed at least 12 weeks before overseeding and no sooner than 8 weeks after.

Should You Fertilize Before, During, Or After Overseeding?

You can overseed and fertilize in any order, although many choose to do them simultaneously to save time.

In the case of doing these steps separately, they should be done within 3 days of each other.

Fertilizing Before Seeding

This process is about as straightforward as it gets.

Fertilize within a few days after aerating, then follow up within 3 days with the overseeding.

How To Fertilize While Seeding?

Measure out the amount of grass seed and starter you’ll need and mix them thoroughly before adding to the lawn spreader.

You can then use the spreader, as usual, starting with an east-west pattern before switching to north-south for even coverage.

Not only is this method easy, but it can save a lot of time by merging otherwise repeated steps.

Fertilizing After Seeding

Try to overseed within a few days of aerating to ensure the ground is still nice and porous.

Follow this with fertilizer either immediately after or within the next three days.

This is also the best time to rake in some compost, as it will not only fertilize your freshly sown seeds but can provide an insulating layer to help prevent the seeds from drying out.