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What do you need to do to overseed a lawn?

Overseeding is the process of adding grass seed to the lawn without turning the soil. Doing this helps add color and thickness to the overall lawn. It also prepares the lawn for harsh seasonal changes that may occur in your region. By overseeding, you can also repair damage from insects, fill in sparse areas or bare patches and help the grass recover after a long drought or other harsh conditions. 

How to overseed a lawn


powered electric dethatcher

For the sake of consistency, start by getting grass seeds that are similar to the existing grass. If you want to change it up instead, get a variety of grass seeds that grow in your area.

Once you have the seeds, mow the lawn until it’s around two inches tall. Next, dethatch the yard. Dethatching is the process of removing “thatch” from the yard. This includes debris, clipped grass and other organic matter. Dethatching is important because it gives room for essential resources like water to get through to the roots. It also helps water drain better for a healthier lawn. To dethatch a smaller yard, use a metal thatch rake. For a larger yard, consider using a powered electric dethatcher instead.

After removing all the thatch, it’s time to aerate the yard. Aerating is the process of loosening up the soil by digging holes in strategic locations throughout the yard. This is a great way to help seeds and any currently growing grass grow without being cramped or choking itself out. Aerating also allows oxygen, water and critical nutrients to reach the grassroots to help them become stronger.

manual aerator

If you have a smaller yard, then a manual aerator may work best. However, if you have a larger yard and can attach the aerator to a lawnmower or other machine, a tow-behind aerator may be better.

pH test kit

When you’ve finished dethatching and aerating the lawn, check the soil’s pH level with a pH test kit to make sure it’s in balance. If the soil is too alkaline or too acidic, the grass won’t be as healthy, thick or lush as it could be.

If you’ve been fertilizing your lawn, stop a month or so before overseeding, allowing the new seeds to grow.

Begin overseeding

lawn spreader

Now, it’s time to start spreading the grass seeds. For small yards, you can do this by hand. But for larger yards, consider using a lawn spreader to cover the yard with seeds efficiently. Make sure you use grass seeds that will grow in your region and climate before starting.

lawn starter or combination fertilizer

A few days after overseeding, use a lawn starter or combination fertilizer to help the new seeds take root and grow. These fertilizers contain phosphorus, nitrogen and potassium, making the grass stronger and more likely to survive in harsher conditions. Look for a fertilizer with high phosphorus content for new grass. Around six weeks later, apply fertilizer made for more mature grass to keep the lawn lush, healthy and green.

handheld water hose with a multifunction nozzle

For the first few days after overseeding, lightly water the yard twice a day. After about a week, start watering the yard every other day for another week or two. A handheld water hose with a multifunction nozzle or a sprinkler with a timer can be a lifesaver during this time. Once the new grass starts to come through, it should be safe to water the lawn as you normally would to prevent wilting.

While the new grass grows, limit activity in the yard to prevent trampling it. Wait to mow the yard until the new grass matches the length of the mature grass. At that point, you may resume lawncare maintenance as usual.

When is the best time to aerate and overseed a lawn?

This depends on several factors, including your region, climate and the type of grass. After all, certain grasses thrive while others start to thin out as the seasons change.

For southern regions, the best time to dethatch, aerate and overseed a thinning lawn is between late spring and the middle of summer. This is because warm-season grasses need a higher soil temperature to germinate and grow properly.

If you live in the north or colder regions, the ideal time to overseed the lawn is during fall when the air is starting to become cool, but the soil is still somewhat warm. During this time, there are fewer weeds for the new grass to compete with for resources.

What grass seeds are best for overseeding a lawn?

Although it’s possible to mix certain grasses and have them thrive, doing this usually results in long-term problems. For one thing, different types of grass may compete for resources, which could cause some grass to be lush while other grass starts to die. For another, some grasses don’t look well together. So, adding new grass seeds of a different variety of grass could make the yard look disorganized.

Find out what type or types of grass are native to your region. For example, fine fescue consists of various species of grasses that have hair-like blades. These are cool-season grasses that grow commonly in the northeast and mid-northern regions of the United States. Fine fescue does not fare well in direct sunlight or hot climates.

If you live in the south and have a lot of bermudagrass in the yard, then you could use cool-season grass like annual ryegrass or turf-type fall fescues to overseed. Another good option if you live in the north is cool-season grass like Kentucky Bluegrass or Perennial Ryegrass. These can withstand moderate summer temperatures and frigid winters fairly well.

In general, people don’t use warm-season grasses to overseed their lawn unless they’re trying to repair a dominant warm-season grass that already grows there. That’s why you’ll most likely want to use cool-season grass that fits your region instead.

Final tips on overseeding a lawn

Here are some final tips on how to best overseed a lawn.

  • Prepare the area in advance by dethatching and aerating it to ensure the new grass seeds germinate and take hold without a problem.
  • Avoid using the wrong type of grass seed for your region, as this may cause problems with the existing grass and keep the new grass from becoming lush and healthy.
  • When using a grass seed package, follow the recommended amounts on the back to avoid spreading more seed than you should. Too much seed could result in the grass competing for resources and the newer grass struggling to survive.
  • Measure out the size of your lawn before starting the overseeding process to make sure you have enough grass seed, fertilizer and other resources available.
  • Never use weed and feed treatments or pesticides while overseeding. Doing so will likely cause the new grass to die before it even begins. 

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Angela Watson writes for BestReviews. BestReviews has helped millions of consumers simplify their purchasing decisions, saving them time and money.

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