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How to Overseed a Lawn

Three Parts:Dethatching and LooseningPrepping the SoilSpreading and Nurturing the Seed

Overseeding is one of the most important tasks involved in growing a healthy, lush lawn. While fertilizing your lawn is important, grass plants slow down their rates of reproduction after a few years. Over time, lawns that have not been overseeded will grow thin and unhealthy, making it much easier for weeds to overtake the lawn. Overseeding can be time-consuming if you have a large lawn, but it is not difficult, and the results are well worth it the effort. This article explains how to overseed a lawn.

Part 1
Dethatching and Loosening

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    Choose the right time of year to overseed. Arguably the best time to overseed is during September, right before winter starts taking root.[1] If you can't overseed in September, overseed in early spring.
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    Mow your existing lawn. Mow your lawn down to a height of 1 to 1 1/2 inches (2.54 to 3.81 cm) in order to minimize competition from grasses and weeds already established in your lawn. Mowing the lawn short will also help keep grass seeds from getting trapped in tall grass and will allow more sunlight to reach the new seedlings. Remove all grass clippings.
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    Rake up the thatch and grass clippings. Thatch is a layer of mostly dead organic matter on the top of the soil.[2] A heavy layer of thatch will keep seeds from germinating, as seeds need to be in direct contact with the soil in order to germinate.
    • Go over the top of your soil lightly with a thatch rake. This process is called "dethatching." If you can't find a thatch rake, you can use a leaf rake, although you may have to rake a little harder in order to remove the thatch.
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    Loosen the soil using the most appropriate method based on the compactness of your soil. Options for loosening the soil include roto-tilling, aerating, or heavy raking.
    • Although roto-tilling is common practice when seeding a new lawn, it is also helpful for overseeding. The only difference between roto-tilling before overseeding and before planting a new lawn is the depth: overseeding requires only tilling about 1 or 2 inches into the soil, while new lawns require 4 to 6 inches.
    • Aerate the soil using a broadfork, being careful not to break the underlying structure of the soil too much. Breaking the soil open hurts the root structure of the existing grass and gives new weeds a chance to invade.

Part 2
Prepping the Soil

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    Conduct a soil test to determine the pH of your soil (optional). The ideal pH level is between 6.0 and 6.8. If you don't know how to perform a pH test, you have two options:
    • You can buy a kit and perform the test yourself, according to direction on the labeling.
    • You can hire a professional or ask your local city to perform a pH test for you.
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    Apply lime to your lawn (optional). Lime will help balance out the pH, if necessary. carefully follow the instructions on the packaging to determine the amount of lime needed based on the pH and the size of your lawn.
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    Top-dress the soil with additional compost. Topdressing is the process of adding a thin layer of compostable material to the top of the lawn. The compost will help the seeds germinate and give the seedlings added nutrients with which to thrive.
    • Lay a very thin layer of compost over the entire surface of the lawn. Too little is better than too much. Too much compost and your existing grass will effectively be buried under compost and die.
    • Spread the compost out evenly over the entire surface of the lawn with a rake, preferably a thatch rake. Make sure that compost does not remain on the top of the grass. Remember to rake lightly when spreading the compost with your rake.

Part 3
Spreading and Nurturing the Seed

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    Spread grass seed evenly over the entire lawn. Use the amount specified on the seed packaging, based on the size of your lawn. To seed, you can either use a rotary spreader, a drop spreader, a hand spreader, or spread by hand.
    • Make sure you choose a variety of seed that blends nicely with your existing lawn. Bermuda grass might be great, but it probably doesn't blend all that nicely with Fine Fescues.
    • It's best to stay away from cheaper brands of seed. You really get what you pay for. If you decide to economize too much, your lawn may carry the telltale sign.
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    Lightly rake the newly seeded area to help the seeds settle on the soil. Remember that any seeds that do not come into direct contact with the soil will not germinate.
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    Apply a slow-release nitrogen fertilizer. Make sure you use a fertilizer that's appropriate for your specific lawn conditions, as indicated by the soil sample results.
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    Water the lawn completely immediately after overseeding. Continue to water the lawn frequently, 3 to 4 times daily for at least the first several weeks to ensure proper germination. Once the grass seed is firmly established, water the lawn for longer periods less frequently.
    • In the beginning, it helps for the seeds to be moist or damp almost around the clock. This will help them germinate. After they have germinated, too much water can eventually kill the seedlings.
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    Apply quick-release nitrogen fertilizer. Use a quick-release fertilizer at a rate of about 1 lb (.45 kg) per 1,000 square feet about 5 weeks after the seeds have germinated. Spread another application of quick-release nitrogen fertilizer 6 weeks later.
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    Mow the lawn once it reaches 2 to 3 inches (5.08 to 7.62 cm). Continue to mow the lawn to a height of 2 inches (5.08 cm) for the remainder of the season.


  • Once grass seed has been spread and moistened, do not let it dry out. The newly laid seed must be kept moist until the seeds have germinated.
  • Equipment you need to loosen and/or aerate the soil can generally be rented from a local home improvement store or equipment rental center.
  • You may be able to get a low-cost or free soil sample kit and analysis done. Contact your municipal government center for information on services that may be available in your area.
  • Keep people and pets away from the newly seeded lawn until the new grass is growing.
  • Core aeration increases contact between seeds and soil, improving germination and helping establish the new grass more quickly. Using a vericutter, also known as an over-seeder, also helps loosen the soil by creating vertical grooves that also increase seed to soil contact. When using a vericutter, make 2 to 3 passes in different directions to create a cross-hatch pattern for better coverage.
  • If you plan to kill weeds, ivy, or other vegetation in your lawn, complete application of any weed-killing chemicals at least 5 days before overseeding.

Things You'll Need

  • Lawn mower
  • Rototiller or aerator, if needed
  • Sturdy rake
  • Soil test
  • Lime
  • Slow-release nitrogen fertilizer
  • Quick-release nitrogen fertilizer
  • Grass seed
  • Seed spreader
  • Garden hose

Article Info

Categories: Gardening | Soil Chemistry