Can You Fertilize and Seed at the Same Time?

side by side image of person fertilizing and overseeding a lawn

For the fertilizer to be effective and not harm the grass seeds, you shouldn’t fertilize and seed at the same time. You need to wait until the seeds begin to sprout, which usually takes about six to eight weeks.

When you fertilize and seed all at once, it’s like feeding solid food to a newborn. Fertilizers can help with the growth and establishment of a newly seeded lawn, but the sudden boost in nutrients can be too much for the seeds and sprouts to handle.

What happens if you fertilize and seed at the same time

Fertilizer for grass, lawn, meadow in a bag of white granules on a background of green grass
Shutterstock

Here are some of the issues you’ll likely encounter if you still decide to fertilize and seed at the same time:

  • Hindrance to growth: Proper seed placement helps minimize uneven grass growth while ensuring an even distribution of soil nutrients. So, if you spread or spray fertilizer while seeding, you risk disturbing the soil and displacing the new seeds.
  • Poor seed germination: If you’re fertilizing and overseeding an existing lawn, doing these tasks all at once can make the seeds and established grass compete for nutrients. This could negatively impact the seed germination and hamper the growth of the existing grass.
  • Wrong nutrients: Choosing the right formula of fertilizer will heavily depend on the soil test results as well as the specific stage of the grass growth. Since the nutrient requirements of seedlings are different from those of an established grass, applying a general-purpose fertilizer during seeding may not be the optimal choice.

Pro tip: If you have no choice but to seed and fertilize simultaneously due to a lack of nutrients in the soil, you can use a slow-release fertilizer. According to Edward Gilman of the University of Florida’s Institute of Food and Agricultural Sciences, using a slow-release fertilizer is unlikely harmful to plants. However, you must apply it as directed on the packaging label.

Optimal way to fertilize and seed your lawn

spreading grass seed by hand
dean | Adobe Stock Free | License

Just as the seasons follow a natural order, so should you follow a specific order to reap the most benefits from fertilizing and seeding your lawn. And it all starts way before the grasses appear.

Experts recommend planting seeds in late summer or early fall. To get the best results, follow these lawn care steps:

  1. Remove thatch: Clear out the layer of dead grass from your existing turf to make the next step (aeration) more effective. It also will allow the seeds to penetrate the soil and establish their roots more easily.
  2. Aerate the soil: Puncturing holes in the ground will help air, water, and nutrients flow more easily in the soil. By aerating your lawn before seeding and fertilizing, you make it easier for the nutrients to get absorbed by the seeds.
  3. Seed or overseed your lawn: When placing new seeds, remember not to overcrowd them or this will stunt growth. Instead, scatter them evenly with the use of a lawn spreader. For best results, hire a pro to seed your lawn – it only costs around $0.09 to $0.19 per square foot.
  4. Water deeply: As soon as you’re done planting, start deep watering for five to 10 minutes. Do this two to three times a day until new sprouts appear to ensure the soil remains moist.
  5. Applying fertilizer treatment: After six to eight weeks, your seedlings should now be able to fully absorb the nutrients from the fertilizer without choking, so it’s safe to apply the fertilizer this time around.

Pro tip: Since professional lawn fertilization costs just around $0.02 to $0.07 per square foot, you can hire a lawn care expert to apply the fertilizer on your behalf. These experts know which fertilizer to use and the right time to apply it.

Best fertilizer to use after seeding

Lawn fertilizer being spread with a manual fertilizer spreader
Shutterstock

When it comes to determining the best fertilizer to use after seeding, the answer will rely on your grass type and the results of your current soil test. Check out the best lawn fertilizers for some of the most common grass types:

Whether you decide to go for organic or inorganic fertilizer, the goal is to pick a formula that will help compensate for the nutrients lacking in your soil.

Since nitrogen and phosphorus are very important nutrients that can help your new grasses thrive, don’t forget to raise them to the recommended levels. Most of the time, any starter fertilizer with high phosphorus content, such as 10-10-10 or 20-10-10, is enough to help boost the growth of your seedlings.

Initially, you can apply a quick-release fertilizer to help green up your new lawn quickly and push the top growth fast so they can block weeds. As your turf starts to get established, consider using a slow-release fertilizer to minimize nutrient burn.

Also, if you’re planning to sow seeds in the fall, you should avoid adding late summer lawn fertilizers beforehand. While these fertilizers are great in keeping existing grasses healthy during their dormant phase, adding them this early will be too much for the seedlings to handle.

FAQ about fertilizing and seeding

Can I put a lot of grass seeds in one spot?

No, this practice is not advisable. While it may seem like a good idea, the result may be contrary to your desire for a thick and lush lawn. Too many grass seeds in the same spot means they will be competing for nutrients, which could stress the sprouts at this early growth stage.

Should I water after I fertilize and seed my lawn?

Yes, it’s necessary to water after you fertilize and seed your lawn. After seeding, you’ll need to water your lawn two to three times a day. Then, once the lawn is established, you can lessen the frequency of watering to about two to three times a week. Note that you’ll also need to water your lawn after applying fertilizer so the soil will not dry up.

Do seeds germinate faster if fertilizer is applied?

Seeds don’t necessarily germinate faster with fertilizer, although it’s quite usual to find seed starter mixes combined with them. For best and safer results, it’s better to wait until seeds germinate before applying fertilizer so as not to shock and stress them out.

Let the experts fertilize and seed your lawn

Having a healthy and lush lawn starts right before the sowing of grass seeds. Plus, there are more things to do when it comes to maintaining a lawn. You don’t have to do all these yourself, though. Let Lawn Love connect you with a local lawn care pro who can help fertilize and seed your lawn at the right time.

Source list:

Main Image Credits:
Fertilizing: Khaligo | Adobe Stock | License
Seeding: rades | Adobe Stock | License

Melanie Joseph

After discovering her passion for writing through her beauty blog, Melanie left her engineering job in California, became a writer, and never once looked back. When she isn't writing, she loves dipping in the pool, tending to the garden, or doing simple home improvement projects.