Overseeding in Spring

replanting grass seed

The technique of overseeding in spring involves planting new grass seed into an existing lawn while taking care to avoid tearing or damaging the turf. This is an excellent method of closing up bare spots that appear during winter and enhancing turf density and color for the new growing season.

Still, spring is not the best time to overseed for all types of turfgrasses. Read on to find out if it is a good choice for your lawn, how to do it with excellent results, and the best way to deal with weeds when overseeding in spring.

What is overseeding

Photo Credit: schulzie | Canva Pro | License

Overseeding is planting grass seeds into an existing lawn without tearing and damaging established grass or turning over the soil. It is a great way to revive a messy, worn-out lawn and a simple and affordable technique to:

  • Fill bare or thinned patches
  • Make the turf denser
  • Improve the lawn’s color and appearance
  • Add more resilient grass varieties to your lawn, increasing pest, disease, traffic, and drought tolerance

Best time to overseed by grass type

Map of the United States showing cool-season grass, warm-season grass, and transition zones.
Infographic by Juan Rodriguez

Late spring and early summer are the best times of year to oversee warm-season grasses. Thriving in warm climates, with hot summers and mild winters, they are the best turf choices for homeowners in the southern states and part of the transition zone.

Warm-season grasses best germinate and grow roots when soil temperatures rise between 65 and 75 degrees Fahrenheit; by this time, air temperatures consistently stay in the 80s.

 Here are the most common warm-season grasses:

In the northern parts of the U.S., late summer to early fall is the ideal season for overseeding cool-season lawns. Cool-season grasses can withstand cold winters and thrive in climates with moderate summers.

In the fall, the soil is warm enough for cool-season grass seeds to provide good germination rates, and the cooler nights protect the new grass from heat stress.

For cool-season grasses, spring is the second option for overseeding your lawn. If you haven’t overseed your property in the fall, you can still do it in early spring when soil temperatures reach 50 to 65 degrees Fahrenheit. You’ll need to keep a tight schedule so new plants have plenty of time to germinate and get established until the summer heat comes.

Here are the most common cool-season grasses: 

Step-by-step guide to spring overseeding

Overseeding in spring goes better if you know a few lawn care tips specific to this season. To get the best lawn retrofit from your overseeding effort, follow these steps and overseeding techniques:

1. Correct existing lawn problems

soil test showing a color chart for soil pH
Photo Credit: CSIRO | Wikimedia Commons | CC BY 3.0

There’s a reason your lawn is thinned out in the spring with bare or brown patches. It might be simply underwatering, a pH imbalance, overfertilization, or soil compaction. But it also can be a fungal infection or nasty pests like grubs or chinch bugs.  

Before overseeding this spring, do your best to identify and correct the cause. This way, you ensure your lawn grows thick and lush and your newly planted grass doesn’t have the same brownish fate. 

Test the soil to check pH and fertility. Acidic soil can be amended with lime, while alkaline soils need treatments with elemental sulfur. The soil test results also tell you what nutrients are lacking or in excess in your lawn so you can use the right lawn fertilizer when overseeding.

2. Mow the grass low

About a day or two before overseeding your lawn, mow the grass 1 ½ to 2 inches tall. But don’t scalp the turf. 

A close-cut lawn:

  • Helps more seeds pass through the grass foliage and reach the soil.
  • Exposes the soil to more sunlight, warming it up and helping germination so grass seedlings grow faster. 

After mowing, rake your lawn and bag the grass clippings. This also will remove dried or dead grass, twigs, leaves, and debris. 

3. Aerate and dethatch, if necessary

illustration showing how aeration works and the benefits of aerating soil
Infographic by Juan Rodriguez

Opinions are divided when it comes to aeration as a way to prepare the soil for overseeding. Some say you must core aerate, even multiple times. Others say dethatching or power raking is enough, and you can overseed without aeration.  

If the soil is compacted, you should aerate it as part of your spring lawn care routine. Aeration loosens the soil, making it easier for grass roots to grow. It also improves airflow, allowing water and nutrients to percolate more easily into the ground and feed grass roots. 

Dethatching removes the layer of dead organic matter (dead grass, roots, leaves, etc.) that forms a dense mat over the soil. Thick thatch prevents grass seeds from reaching the ground and needs to be removed before overseeding. 

Aeration removes some of the thatch, but not all. Whether you aerate or not, you still need to dethatch or power rake the lawn. 

You can remove the thatch using a dethatcher or a scarifier. 

  • Dethatchers have spring tines that softly rough up the topsoil when used at their lowest setting. They break up thin to moderately thick thatch layers and lightly loosen the dirt.
  • Scarifiers have metal blades and cut deeper into the soil, breaking up thicker thatch layers with less effort. 

Finish this step by raking the organic debris from your lawn. Raking also helps break up the soil surface, making it easier for grass seeds to root.

4. Choose the best grass for your lawn

Keep the same mix or upgrade the lawn: If you’re happy with your turf, try to find and apply the same grass mix growing in your lawn. 

The other option is to take advantage of spring overseeding and upgrade your turf with more resilient grass varieties. For example, you can overseed the shaded areas of a ryegrass lawn – ryegrass needs full sun to thrive – with varieties that have a better tolerance for shade, like tall fescue and fine fescues. 

Choose only grasses suitable for your location: Seed a turf type compatible with your climate to ensure a thriving, low-maintenance lawn. Cool-season grass seed types are the best choice in northern, eastern, and western sections of the U.S. Warm-season grass types grow well in the southern, southeastern, and southwestern regions. 

Consider timing: Perennial ryegrass germinates in 5 to 10 days. The fast germination makes it an excellent grass for spring seeding when newborn plants have only a limited window to get strong enough for summer. 

Kentucky bluegrass germinates much slower. It needs 14 to 30 days to show any signs of growth. If you’re late with your spring overseeding, few of the new sprinklings will survive the summer heat, and you’ll need to overseed again in the fall.

Pro tip: Look for good-quality grass seed with a high germination rate, over 75%.

5. Prepare the right amount of seed

sparse grass in need of overseeding
Photo Credit: John Mounsey | Pixabay | License

Applying too much seed may cause overcrowding as new grass seed sprouts. The stronger grass sprouts will survive, but they may choke out existing grass, which will lead to the need to perform additional overseeding.

Measure the lawn or the overseeded area to determine how much grass seed you need. For example, if you’re overseeding a thinned area in the driest corner of your yard, you’d measure like this:

  • Stick some stakes in the ground around the area you plan to overseed to define a rectangle.
  • Measure the rectangle’s length and width using a measuring tape. Let’s say it is a 40 ft. by 100 ft. patch.
  • Multiply the length by the width, and you’ve got the size of the area you’ll overseed. In our example, the area is 4,000 sq. ft. (40 ft. x 100 ft.)

With larger or more complicated areas – like your entire yard – divide the surface into several rectangles. Measure each rectangle’s area following the above steps and add the numbers.

Next, determine the seeding rate – the seed amount per 1,000 sq. ft. It helps to know what product you’re buying at this stage. If not written on the seed package, follow these general rules:

  • If most of your lawn has thick grass growth, overseeding will be a general maintenance task. Use 2 to 4 pounds of seed per 1,000 square feet of lawn. 
  • If your lawn has bare patches, apply 4 to 8 pounds of seed per 1,000 square feet. 
  • For lawns that need complete renovation, 8 to 12 pounds of new grass seed for every 1,000 square feet of turf will be required.

To calculate the necessary amount of seed, divide the total measured area by 1,000 and multiply it by the seeding rate. For our example of 4,000 sq. ft. and a seeding rate of 6 pounds per 1,000 sq. ft., you’d calculate like this:

4,000 sq. ft. /1000 sq. ft. * 6 pounds = 24 pounds

6. Spread the grass seed

You’re ready to overseed your lawn. What you need to do now for your DIY overseeding is choose the proper tool for your lawn:

  • You can use a handheld seeder for small patches. 
  • Drop seed spreaders are popular choices for small to medium-sized lawns. They release grass seeds directly under, providing excellent precision. 
  • Broadcast spreaders are more effective on larger lawns. They throw the seeds wider, providing better coverage and speed but less precision. 

When spreading the grass seed on your lawn, follow these steps:

  • Fill your seed spreader with grass seed. 
  • Set the seeder at half the spreading rate indicated on the seed bag.
  • Spread half of the amount across the area you want to overseed, going back and forth with a steady pace.
  • Change the walking direction by 90 degrees and repeat the previous step, spreading the second half of turf seeds.
  • Use the back of a rake to mix the seed into the topsoil.

Should you topdress the lawn before or after overseeding? This is another disputed subject. Grass seed needs fertile ground, good contact with the soil, and benefits from a high-quality top dressing added to the lawn. But, grass seed should not be covered with a layer thicker than ⅛ to ¼ inch. 

You can spread compost or a topdressing mix:

  • Before overseeding in a layer no thicker than ½ inch (to avoid damaging established turf).
  • After overseeding, but in a thinner layer of up to ¼ inch deep.

Pro tip: Peat moss is a good top dressing that also tells you when it’s time to water the seeds by changing its color – peat turns from a dark, almost black color when wet to a light brown when dry. 

7. Water daily until seeds germinate

sprinkler on grass shooting out water
Photo Credit: Shaylor | Flickr | CC BY 2.0

Grass seeds need constant moisture to germinate. Lightly water the seeded areas at least twice daily until the grass germinates (two to four weeks). Keep the sprinklers on for about 10 to 15 minutes minutes each time. This typically adds up to 3-4 inches of water per week, with 1/8 to 1/4 inches applied each session. 

How much water you need during germination depends on the weather, soil type, water pressure, and sprinkler flow rate. Do your best to keep the top 1-2 inches of soil moist (not soggy) and prevent seeds from drying out.

Pro tip: If you’re overseeding on a lawn with established grass, give it a deep watering once a week to support the roots.

After all the seeds germinate, gradually reduce the frequency and increase the amount of water you apply each time. Do this across one to two weeks until you arrive at the regular irrigation schedule of watering once or twice a week with 1 to 1.5 inches of water per week. Water the lawn deeply each session to moisten the top 6 to 8 inches of soil and promote strong roots. 

8. Fertilize the grass

New grass also needs extra nutrients. Apply a starter fertilizer before or right after overseeding the lawn. Starter fertilizers have a small amount of phosphorus that helps grass sprouts develop healthy roots. 

Pro tip: Don’t use a weed and feed when overseeding the lawn. The herbicide included in the formula affects grass germination and growth.

How to control weeds when overseeding in spring

With warm-season grasses, there’s usually enough time to make one application with pre-emergent herbicides in early spring to control crabgrass, foxtail, nutsedge, knotweed, and other nasty weeds

Most pre-emergent weed killers remain active for 9 to 12 weeks, preventing any seed from developing roots and properly germinating. If you apply a crabgrass preventer in early March, you should be able to overseed safely in late May or June.

Cool-season grasses have a shorter time window for establishing and can’t wait that long. In this case, the best options for weed control are:

  • Hand pulling – when sprouted weeds are in small numbers. 
  • Selective herbicides – ingredients like mesotrione and topramazone that are safe for new seedlings if applied correctly. 

Pro tip: If you already treated the lawn with a regular pre-emergent, postpone overseeding for the period indicated by the product manufacturer.

Overseeding methods  

You can use two types of overseeding methods to refurbish your lawn:

  • Broadcast seeding, also known as over-seeding.    
  • Slit seeding or slice seeding.

Broadcast seeding 

Man seeding and fertilizer a residential lawn
Photo Credit: Shutterstock

Broadcast seeding is the standard choice for routine overseeding on lawn areas with more than 75 percent grass coverage. Homeowners also use it for renovating severely damaged lawns, but pros often replace it with split-seeding in this case. 

How to overseed with a broadcast seeder: Start by dethatching the lawn. Use a dethatcher at its lowest setting to loosen the top of the soil and rake the debris.

Some landscaping professionals prepare the soil for broadcast seeding by aerating it multiple times. Aeration also loosens the thatch layer and helps you remove it. If you want to try this method, space the aeration holes no more than 2 to 3 inches apart. For best seed-to-soil contact, remove soil plugs with core-style aerating tines. 

If you use core aeration, choose grasses with a creeping growth style, like bluegrass, to obtain even grass growth. With grass varieties that will not spread, the new grass will sprout in the aeration holes, leaving the lawn clumped or tufted. 

Slit seeding 

Slit seeders have verticutting blades that slice through the thatch and ground soil to create a slit or mini-groove (or small trench) where the seed is dropped to germinate.

This overseeding method provides the proper distribution of seed directly into the soil without any loss of seed through scattering. It ensures high germination rates, resulting in more attractive new grass growth.

How to use a slit seeder: The depth of the slit should be no more than one-half the length of the grass seed husk and varies with the type of grass seed. 

Many lawn growth experts recommend overseeding each turf area twice (making two passes). Each pass should seed at 50 percent of the overall rate recommended for your lawn. 

If you make both passes at a 45-degree angle to one another, forming a pattern similar to the shape of a diamond, each set of seeds will be placed in the soil approximately 2 inches apart. 

Benefits of overseeding your lawn

Top-quality overseeding spring lawn techniques can provide significant benefits for older or worn-out sections of turf, such as: 

Improved appearance: Adequate and timely overseeding in the spring replenishes the earlier growth of rich green grass without damaging or disturbing the surrounding healthy turf. It supports a thick, green lawn and improves your property’s curb appeal.

Natural weed control: Worn-down lawns quickly become overgrown with weeds. Overseeding the lawn helps the grass grow denser and smother weeds, preventing weed germination and growth.

Better drought, shade, and traffic resistance: Many lawns surrounding older homes were initially seeded with grass varieties incompatible with modern lawn use, wear, and upkeep. By overseeding with a more resilient variety, you can increase the lawn’s tolerance to drought, shade, and heavy foot and equipment traffic.

Less need for fertilizers and water: Worn-out turf requires more fertilizing and watering to grow. Overseeded lawns have vigorous, healthy plants that can thrive with fewer resources.

Preventing soil erosion: Bare patches and thinned lawn areas expose the soil to erosion and nutrient loss. When overseeding, the new grass you plant develops healthy roots that keep the topsoil in place. Dense grass also slows down rainfall and captures rainwater, reducing runoff.

Pros and cons of spring overseeding

Late summer and fall are the best times for overseeding cool-season grasses. Spring overseeding is the second option and comes with some drawbacks:

  • There’s a shorter window for cool-season grasses to germinate and establish roots strong enough to keep the grass alive during the summer heat.
  • The soil is colder, and germination takes longer.
  • Weed competition is higher in the spring and can easily overwhelm new seedlings.
  • Young, barely established cool-season grass needs lots of water during the summer to survive its first hot season.

These being said, there are also some good parts to spring overseeding:

  • It allows you to repair patches that appear during winter and make the lawn beautiful for the coming outdoor season.
  • Areas under deciduous trees are in full sun until their leaves start growing. It’s the best time to grow healthy grass in sections of your yard that are typically in the shade.
  • In many areas of the country, spring benefits from enough rainfall to drastically reduce the need for watering during germination.

FAQ about overseeding in spring

What are the best grass seed mixes for overseeding a lawn in spring?

The best grass seed mixes for overseeding a cool-season lawn in spring are:

  • Kentucky bluegrass with turf-type tall fescue
  • Kentucky bluegrass with fine fescue and perennial ryegrass 

They provide good tolerance to sun, shade, traffic, and wear.

What is the ideal soil temperature for overseeding my lawn in spring?

The ideal soil temperature for overseeding a lawn in the spring is 50 to 65 degrees Fahrenheit for cool-season grasses and 65 to 75 degrees Fahrenheit for warm-season grasses.

How to topdress and level your lawn?

If you have depressions in your lawn where water puddles, spring overseeding is the perfect time to level the ground. Here’s how:

  • With deep areas, simply apply enough topdressing mix to level the area. Compact it and add some more if necessary, even if covering the existing grass. Then, overseed the area.
  • If the low spots are superficial, add a thin layer of topdressing, up to ½ inches thick. Spread it even with a rake, then use a broom to clean the dirt from the grass blades. Repeat later on the spot is still a bit lower than the rest of the lawn. 

When to call a professional

Overseeding a cool-season lawn in the spring is difficult because conditions are not ideal. If your lawn has large areas of bare soil, you’ll want an experienced professional to do the job and provide you with the best lawn possible. With Lawn Love, the best lawn care professionals are only a click away! Use our website to connect with a lawn care company in your area and get your lawn overseeded today!

Main Photo Credit: tab1962 | Canva Pro | License

Sinziana Spiridon

Sinziana Spiridon is an outdoorsy blog writer with a green thumb and a passion for organic gardening. When not writing about weeds, pests, soil, and growing plants, she's tending to her veggie garden and the lovely turf strip in her front yard.