What is Overseeding? How to Overseed for Great Results

What is Overseeding? 
How to Overseed for Great Results

Dead spots stick out — seasons of drought and disease strip luster from lawns. There is a helpful solution: overseeding. But what is overseeding?

Let's take a look at the process. We'll cover some of the following:

• What is overseeding?

• Why Overseed a Lawn?

• The benefits of overseeding

• How to overseed your lawn

• When to overseed your lawn

Key Takeaways:

What is Overseeding?

Overseeding refers to planting new grass seed over an existing lawn. Unlike seeding, which usually means starting over from scratch, overseeding works with the grass you already have, helping to fill in thin spots, improve lawn density, and introduce newer, more hardy varieties.

It's easy. There's no turning the soil in the process. 

You seed directly on existing turf. It's a great way to rejuvenate your lawn and make it thicker, healthier, and more resilient. It's the perfect way to eliminate bare spots in your yard and add some lushness back to your grass.

When you overseed, new grass seed germinates and grows among the older grass blades. The new grass interacts with the old, creating a more uniform, stronger, and better-looking lawn.

Why Overseed a Lawn?

You'll get a lot of rewards from overseeding: it will thicken your lawn, creating a lush carpet that looks good and is less susceptible to weeds. Overseeding also improves your lawn's color, giving it a dense green look. An overseeded lawn will be more disease- and drought-resistant, which means less need for chemical or organic treatments to control diseases and less compulsive watering to keep the grass green.

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Overseeding can revive a thinning or patchy lawn, as over time, lawns can become thin in some areas, develop bare spots, or lose their green color. This can be caused by heavy traffic, environmental stressors, or simply aging the existing grass varieties. Overseeding can address these issues by adding new grass seed to the lawn, which will not only fill in the gaps but also improve the overall health and look of your lawn.

When to Overseed Your Lawn

Overseeding is all about timing. Cool-season grasses like Kentucky bluegrass or fescue should be overseeded in the early fall when temperatures are moderate and the soil is still warm enough for the new grass to establish deep roots before winter. Spring is acceptable too, but it will require more diligent watering while the seedlings establish before the heat of summer sets in.

For warm-season grasses, like Bermuda or Zoysia, late spring to early summer is the best time to overseed. These grasses are most productive in peak summer months, so planting in spring gives them time to establish a root system before the weather warms.  

It's important to consider moisture levels and soil temperatures during this process. The warmer the soil, the better for warm-season grasses — ideal soil temperatures are 65 degrees and above.

Cool-season grasses need between 50°F and 65°F for seed germination and mild conditions for new seedlings to grow (avoid overseeding in extreme weather, such as drought or frost).

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Although your lawn may benefit from overseeding every year, the needed frequency varies from yard to yard depending on the health of the lawn, the type of grass, and the growing conditions. Lawns that are persistently thin and constantly patchy may need overseeding every year or two.

A properly maintained lawn might only need overseeding every three or four years. Keep your eye on your lawn. If it starts to look tired or thin, it may be time to overseed.

Preparing Your Lawn for Overseeding

While overseeding is straightforward, a few things can be done to make your efforts even more successful. Here are a few things to do to prepare your lawn for overseeding:

 Soil Testing and Preparation 

While you don't have to test your soil before overseeding, a good soil test will tell you the pH and nutrient levels, so you'll know what amendments you should make before you seed. If your soil is too acidic for seedlings or critical nutrients are lacking, the grass you seed will have difficulty growing. The test might suggest adding lime to balance Ph or a fertilizer high in phosphorus to promote root growth.

 Mowing the Lawn 

Before overseeding, you want to make sure that you mow your lawn very short (down to 1.5 to 2 inches). This opens up more bare soil for the seeds to make better contact with the ground and reduces competition from the existing turf – helping the new seedlings to germinate.

RELATED: How to Get the Amazing Lawn You Want

 Dethatching and Aeration 

Thatch – a layer of dead grass and organic debris accumulating on a lawn – can inhibit seed from reaching the soil, so removing it with a dethatcher is one of the first steps to overseeding. Aerating, which is perforating soil, also allows water, air, and nutrients to penetrate further into the ground and find their way to the seed.

 Clearing Debris 

Make sure to remove leaves, sticks, and other debris from your lawn before overseeding. Why? Debris might prevent seeds from reaching the soil. A clean lawn is an important step to successful overseeding.

How to Overseed a Lawn

Once your yard is prepped, it's time to lay your seed. But do you have the right mix? There are many seed blends on the market, but pick a seed that matches your grass type for a uniform look. If you are going for a different look, choose a different seed variety to introduce new characteristics, such as drought tolerance or disease resistance. Make sure the seed is fresh and the right type for your climate.

Use a broadcast spreader to cover wide areas and a drop spreader for smaller quantities and more precise applications. The seeds should be distributed evenly but densely to ensure the entire lawn is adequately covered. Overlap at the end of each pass so the lawn is full.

Next, scatter the seed and dust on a starter fertilizer high in phosphorus, which is key to root development. Be mindful not to overdo it. Too much starter can add too much salt to the soil and keep the right amount of water from reaching the seeds.

Water is also critical to overseeding. The soil must stay constantly moist to stimulate the seeds to germinate. Water lightly but frequently to keep the top of the soil moist. Avoid overwatering. Runoff displaces seeds. As the seeds take root, gradually reduce the frequency but increase the watering depth to encourage deeper roots as your new grass grows.

How to Care for Your Lawn After Overseeding

Once you've overseeded, there's still some work to do. Caring for the newly established seed will increase your chance of achieving your desired lush lawn. 
Take these steps to help your overseeding efforts:

 Watering after overseeding:  You should water daily for the first few weeks, keeping the soil consistently moist. Once the new grass gets established, resume a more typical watering schedule of once or twice a week.

 Mowing after overseeding:  Wait until the new grass is 3 to 4 inches high before mowing, and then use a sharp mower blade and mow at a higher setting so as not to 'scalp' the tender young grass. Mow often, but be aware of cutting over one-third of the grass blade in a single mow.

 Fertilization and Nutrient Management:  Apply a balanced, slow-release fertilizer six to eight weeks after overseeding. The ongoing nutrition helps the new grass continue laying down roots to become more resilient.

 Weed Control:  You'll want to manage weeds after overseeding, but keep herbicides off newly planted grass, if possible. Pull emerging weeds by hand to prevent competition with the new grass.

Common Overseeding Mistakes to Avoid

Even though overseeding is a straightforward process, there are still a few mistakes you'll want to avoid. One of the most common is overseeding outside the ideal seasonal window for your lawn. This mistake will result in poor results; grass seeded in the heat of the summer will be drought-stressed, and seeds planted too late in the fall will not have enough time to establish before winter.

You can often end up with a patchy, bumpy, uneven lawn if you choose the wrong kind of seed. Be sure to select a grass variety that matches your climate and lawn well. Mixing grass types that are not compatible can lead to growth and color inconsistencies.

And don't leave your efforts to fate: overseeding can be an exercise that's doomed to failure from the start without proper preparation. If your soil is not adequately prepared to receive the seed, seed-to-soil contact will be poor, weakening germination and leading to uneven, thin growth.

Maintenance after overseeding is critical to its success, too. Not watering, mowing, or fertilizing during this time can prevent the new grass from becoming established, negating the whole overseeding process.

Quick Summary

Overseeding is important to maintaining a healthy, full, lush lawn. Overseeding will green up your lawn by filling in bare spots, thickening your turf, and introducing more disease-resistant grass varieties to your lawn.

We explained what overseeding is and why it's a straightforward way to bring vigor back into a yard. Prepping a yard is the first step to a successful overseeding. Ensure you select the right seeds for your lawn — make sure they don't conflict with your current grass and climate. Once you've laid your seed, proper maintenance can boost your chances of success.