After overseeding your lawn, apply a lawn starter fertilizer to provide grass seedlings with the nutrients they need to establish themselves. Do not substitute lawn starter with a fertilizer meant for mature grass. Mature grass fertilizer doesn’t contain the nutrients new grass needs to develop roots. Similarly, avoid using “weed and feed” fertilizers. These products will kill your grass seedlings.
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5 Tips for Fertilizing Your Lawn After Overseeding
Overseeding a lawn takes time and money. Naturally, you want to get the most out of your efforts. In order to ensure your grass seedlings survive and thrive, it’s essential to follow the proper methods. Employ these tricks to make sure your grass seed roars to life.
Use a Lawn Starter Fertilizer
A lawn starter fertilizer is formulated so that of the three main ingredients in fertilizer (nitrogen, phosphorus, and potassium) phosphorus is the most abundant nutrient. This is important because phosphorus drives grass root growth. A lawn starter fertilizer will encourage your grass seedlings to take root quickly. This will make them hardy and established, whether you overseed in late spring or fall.
- Use this lawn starter fertilizer for new grass seed.
- Lawn starter fertilizer has high phosphorus content to promote seedling root growth.
- Do not use a fertilizer designed for mature grass. These often contain little to no phosphorus.
A standard fertilizer used for established lawns does not make for a good lawn starter. These formulas contain very little phosphorus because mature grass has already established roots. Some fertilizers for established warm-season grass lawns even contain no phosphorus at all. If you don’t use a lawn starter fertilizer on your seedlings, they won’t develop strong roots and may die.
Avoid Weed and Feed Products
Weed and feed products are a death knell for grass seed. This is due to the fact that most weed and feed combines fertilizer with pre-emergent herbicide. This type of herbicide attacks all types of plant seeds, killing them as they germinate. If you spread weed and feed on a lawn that has been overseeded in the past 8 weeks, it can kill all the grass seedlings there.
- Weed and feed products contain pre-emergent herbicides that kill grass seeds as they sprout.
- Do not apply weed and feed to a lawn that has been overseeded in the past 8 weeks.
- Do not overseed if you have applied weed and feed in the past 12 weeks.
The herbicide in weed and feed is designed to linger in the soil for up to 3 months. If you have already applied weed and feed, don’t overseed your lawn for at least 12 weeks. The herbicide in the soil will attack every type of grass seed.
Dethatch Before You Overseed
A thick layer of thatch forms a barrier between the grass and the soil. 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 nutrients and moisture from the soil and grass seed.
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. Fertilizing on thick thatch will be far less effective. Removing thatch prior to overseeding helps you deliver more lawn starter fertilizer to your grass seeds.
Aerate Your Lawn
Compacted soil makes it difficult for grass seedlings to take root. Not only that, but fertilizers have a difficult time penetrating hard soil. It’s a good idea to aerate the soil so that it absorbs fertilizer and feeds your grass seeds.
- Hard soil prevents grass seeds from rooting.
- Compact soils struggle to absorb nutrients from fertilizer.
- After dethatching, aerate your soil to make feeding your grass seed easier.
Aeration goes hand-in-hand with dethatching. A recently dethatched yard is ripe for aeration. If you mow, dethatch, and aerate, your entire lawn is in the perfect condition for overseeding.
Boost Seed Growth with Compost
Compost is an excellent natural fertilizer, but there’s one catch—the nitrogen in compost is contained in uric acid, and uric acid evaporates quickly when exposed to light. So, a thin layer of compost spread over your lawn will quickly lose most of its fertilizing power. There is a solution though. If your lawn was recently aerated it has thousands of tiny holes. You can spread compost over a recently aerated lawn to fill these holes and inject nitrogen-rich fertilizer into the soil.
- Compost is a great natural fertilizer that boosts grass seed growth.
- Only spread compost on your lawn if it has recently been aerated. Compost will retain more of its nitrogen content when it is used to fill aeration holes.
- Rake a thin layer of compost over your grass seeds—it may lose most of its nutrients but it will serve as a protective layer to keep seeds moist and safe from birds.
It’s a great idea to spread compost after aerating and overseeding. The compost will fill the aeration holes to funnel nutrients in the soil. Excess compost on the top of your grass seeds will keep them protected from drying out.
Is it OK to Fertilize After Overseeding?
It is perfectly safe to fertilize after overseeding your lawn. In fact, applying a specialized lawn starter fertilizer will increase the number of grass seedlings that survive to adulthood. For best results, apply a starter fertilizer within 3 days over overseeding. This will contribute to a lush lawn.
When Can I Fertilize My Lawn After Seeding?
If you’ve recently overseeded your lawn, there’s no reason to wait to apply fertilizer. The sooner you spread a lawn starter fertilizer on your yard, the sooner it will begin to feed your grass seedlings. If you like, you apply fertilizer the minute you’re done spreading your grass seed.
Do You Fertilize Before or After Seeding?
You can fertilize your lawn before or after overseeding. Both tactics work to feed your new grass seed. It’s best to fertilize within 3 days of seeding. This means you can spread your starter fertilizer a few days before you lay down your seed or a few days after. Both are far more beneficial for a healthy lawn than going without fertilizer.
Can You Put Fertilizer Down With Grass Seed?
If you want to make your seeding and fertilizing processes more efficient, you can spread your grass seed and lawn starter simultaneously. Simply measure out the correct amount of seed and fertilizer for the square footage you are overseeding, mix the fertilizer and seed thoroughly, and add them both to this lawn spreader. Make sure to spread the seed and fertilizer evenly across your lawn, following an east-west pattern followed by a north-south pattern for proper coverage.
Will Fertilizer Kill New Grass Seed?
The only fertilizers that will kill your grass seed are “weed and feed” products. These fertilizers are mixed with pre-emergent herbicide that kills all plant seeds as they sprout, including your grass. Lawn starter fertilizers are formulated without any added herbicide. They will boost your seedling growth with nitrogen and phosphorus without causing any harm.
What Kind of Fertilizer Should You Use When Overseeding?
Use a specialized lawn starter fertilizer to give your new grass seed what it needs to establish itself. An overseeded lawn needs an application of a strong lawn starter to allow it to thrive and take root among the mature grass already present. Don’t use a fertilizer designed for mature lawns because this will not provide your grass seedlings with the nutrient balance they need. Combine overseeding and fertilizer with dethatching, aeration, and compost to further boost the performance of your new grass seed. With these lawn care techniques, you will have an incredible green lawn in just a few weeks after overseeding.