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Overseeding is a practice of planting more than one seed per pot in order to increase the chance of germination and producing a desired crop.
There are many types of fertilizer to use after overseeding, but some factors to consider when deciding which one to use include soil type, crop type, and specific conditions.
Fertilize or Overseed First?
A common question I get is whether to fertilize or overseed first.
If you are looking for low-maintenance lawn care that delivers good results, I advise that you do both steps at the same time.
Simultaneous fertilizing and overseeding are not only possible but also preferable.
Five Tips for Fertilizing Your Lawn After Overseeding
Overseeding a lawn takes time and money. Of course, you want to get the most out of your efforts.
To ensure your lawn seedlings survive and thrive, it’s important to follow the right methods.
Use these methods to ensure your weed seed comes to life.
Remove Thatch Before Overseeding
A thick layer of thatch creates a barrier between the grass and the ground.
If you sow grass seed on a lawn with a lot of thatch, the seed will not reach the ground.
Without ground contact, the grass will not sprout and settle.
Check the thatch layer in your garden and remove any thatch before planting.
Coarse thatch prevents grass seeds from reaching the ground where they can take root.
Rent a dethatcher or electric rake to remove thatch before reseeding.
Grasses are known to form a layer of thatch on the surface.
Thatch is useful because it can help protect roots from sudden temperature changes and is made up of living and dead organic matter that is deposited in the root system in a mat-like manner.
Unfortunately, thatch can also become so thick that it prevents seed, water, and fertilizer from seeping into the soil below.
Thatch absorbs water and fertilizer, removing nutrients and moisture from the soil and grass seed.
Coarse thatch not only prevents grass seedlings from taking root but also acts like a sponge, soaking up water and fertilizer before it can seep into the soil.
Fertilizing over coarse thatch is much less effective. Removing thatch before reseeding will help grass seed get more lawn starter fertilizer.
Read Also: Using Peat Moss for Overseeding a Lawn [Pros and Cons]
Aerate Your Lawn
Another essential aspect of lawn care, soil aeration is essential if you want to get the best seeding results.
It loosens the soil, which allows the seeds to take root, and also helps absorb the fertilizers before sunlight breaks them down.
Aeration is best done after removing the sod and before sowing.
Compact soil makes it difficult for grass seedlings to take root.
Not only that, fertilizers have a hard time penetrating the hard soil.
It’s a good idea to aerate the soil so it absorbs the fertilizer and nourishes the grass seeds.
Hard soil prevents grass seeds from taking root.
Compact soils have difficulty absorbing nutrients from fertilizer.
After shipping, please aerate the soil to make it easier to feed grass seed.
By mowing, cleaning, and aerating, your entire lawn will be in perfect condition for overseeding.
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Use a Lawn-starter Fertilizer
After your lawn has been mowed, weeded, and aerated it’s time to collect seeds and fertilizer, but which fertilizer should you use?
Lawn start fertilizers have a higher phosphorus content.
In flowering plants, to produce flowers, young grasses rely more on phosphorus for healthy root growth.
A lawn-starter fertilizer is formulated so that of the three main fertilizer components (nitrogen, phosphorus, and potassium), phosphorus is the most abundant nutrient.
This is important as phosphorus fuels the growth of grassroots.
The fertilizer encourages grass seedlings to take root quickly.
This will make them sturdy and stable whether you transplant them in late spring or autumn.
Avoid Weeds and Feed
Avoid Weed and Forage Products
Any product labeled as weed and forage is a type of fertilizer that should be avoided at all costs when planting.
This is because most weed and feed products combine fertilizers with pre-emergent herbicides.
This type of herbicide attacks all types of plant seeds while they are germinating.
The pre-emergence fertilizers and herbicides are designed to kill broadleaf weeds and many other unwanted invaders for up to 3 months.
Unfortunately, while these are usually formulated to kill specific plants, weed and feed products do not discriminate when it comes to seeds and will kill your weed seed along with the seeds you don’t want.
To avoid this counterproductive fate, apply and fertilize grass at least 12 weeks before reseeding and no sooner than 8 weeks after.
Weeds and feed are a death sentence for grass seed.
If you have already applied weeds and fertilizer, do not overseed your lawn for at least 12 weeks.
Boost Seed Growth with Compost
Compost is an excellent natural fertilizer, but the downside, however, is that the compost contains nitrogen mainly in the form of uric acid.
Therefore, a thin layer of compost spread over your lawn will quickly lose most of its fertilizing power.
However, there is a solution.
If your lawn has recently been aerated, it will have thousands of tiny holes. You can spread compost over a recently aerated lawn to fill in these holes and inject nitrogen-rich fertilizer into the soil.
Remember that compost application usually works best after overseeding, although it is also effective when used beforehand.
It’s a good idea to spread compost after aerating and overseeding.
Compost fills air holes to draw nutrients into the soil.
Excess compost on grass seed protects it from drying out.
Should I Fertilize Before, During, or After Overseeding?
You can overseed and fertilize in any order, although many choose to do so at the same time to save time.
You can fertilize your lawn before or after overseeding.
Both tactics work to feed your new grass seed.
It is best to fertilize within 3 days of planting. A few days before laying your seed or a few days after.
Fertilize Before Overseeding
This process is as simple as can be.
Fertilize within a few days after aeration, then follow overseeding within 3 days.
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Fertilize During Overseeding
Measure the amount of grass seed and starter you need and mix them well before adding them to the lawn spreader.
You can then use the spreader, as usual, starting with an east-west pattern before moving north-south for even coverage.
Not only is this method easy, but it can save a lot of time by merging steps that would otherwise be repeated.
Fertilize After Overseeding
Try overseeding a few days after aerating to ensure the soil is still nice and porous.
Follow that with fertilizer, either immediately afterward or within the next three days.
This is also the best time to rake in some compost as not only will it fertilize your newly planted seeds but it can also provide an insulating layer to prevent the seeds from drying out.
Will the Fertilizer Kill the New Grass Seed?
The only fertilizers that kill grass seed are “weed and feed” products.
Starter fertilizers are formulated without the addition of herbicides.
They boost the growth of your seedlings with nitrogen and phosphorus without causing any damage.
Which Fertilizer Should You Use When Overseeding?
Use a special lawn starter fertilizer to give your new grass seed what it needs to establish itself.
Root into existing mature grass.
Do not replace lawn starters with a fertilizer designed for mature lawns.
Mature grass fertilizer does not provide the nutrients that new grass needs to develop roots.
Fertilizers for mature lawns contain little or no phosphorus, which prevents germinating grass seedlings from developing a healthy root system.
Similarly, avoid using “weed and forage” fertilizers. These products will kill your lawn seedlings.
Final Thoughts
It is safe to fertilize after overseeding your lawn.
Applying a special lawn starter fertilizer increases the number of lawn seedlings that survive to adulthood.
For best results, apply a fertilizing starter fertilizer within 3 days of sowing. This contributes to a lush lawn.
If you’ve recently over-seeded your lawn, there’s no reason to wait to fertilize.
The sooner you spread a lawn-starter fertilizer in your garden, the sooner it will begin to nourish your lawn seedlings.
If you wish, you can apply fertilizer right after sowing your grass seed.
With these lawn care techniques, you’ll have an amazingly green lawn in just a few weeks after overseeding.
