What is Overseeding?

Overseeding is the task of spreading grass seed directly onto an existing lawn. Many decide to oversee if a lawn is beginning to look thin or worn out. It is also done to choke out weeds by creating a dense, carpet-like lawn. If you are currently coming out of a drought or your lawn is beginning to need more and more fertilizer to keep it looking healthy, then overseeding may be a good option for you. Overseeding is also popular for lawns with old grass species; many new grass variants have been bred to be more resistant to heat or certain pests. Because overseeding does not tear up any vegetation or soil, it is an easy and non-invasive way to fill in bare spots, improve turf density, and enhance your lawn’s color.

What to Watch Out for When Overseeding

It is important to know what grass or grasses are already growing in your yard as well as their condition. For instance, Centipede grass, a warm-season grass, does not do well with overseeding because of its unique root system. All forms of Bentgrass, cool-season grasses, can be overseeded but do not mix well with other species. Because of this, if your yard is made up of Bentgrass, make sure to overseed with the same species. Understanding your lawn’s state is also important because sowing more seeds may not be necessary. If your lawn is already thick, dense, and carpet-like, overseeding may do more harm than good. Doing so will create excessive competition amongst the grass for water and nutrients. Using too large an amount of seeds will have the same result.

The Best Seed for Overseeding

Cool-season grasses work best for overseeding. These include Kentucky Bluegrass, Fescues, Ryegrass, etc. The seed you end up choosing depends on your lawn’s condition and overseeding goals. Each grass species will have its pros and cons, so you can check out our Choosing a Grass Seed article for a more complete guide on seed choice. The first thing to consider when choosing a grass seed is what your lawn is already made of. You may want a lawn that is all the same species for consistency in color and texture. Alternatively, if speed is of the essence for you, Perennial Ryegrass or Tall Fescue may be your best option. Be careful with store-bought, bargain seed mixes; some of them are low-quality and have a combination of seeds that do not pair well with one another.

The amount of seeds you need will depend on the variety you choose. Typically, a bag of seeds will list the ideal overseeding amount along with the amount for a new lawn. Generally, mixes recommend about 2 to 3 pounds per 1,000 sqft when overseeding, but refer to the bags instructions.

Preparing the Lawn for Overseeding

Several steps should be taken before overseeding. Firstly, if you have used any herbicides on your lawn, you will need to wait until they wear off. It should say on your herbicide’s instructions the amount of time before you are able to reseed. A generic herbicide like Weed B-Gon says to wait four weeks before reseeding. Other less powerful herbicides may let you reseed in as little as two weeks.

Before seeding, you should mow your lawn short. Cut the grass to about half its original height, but do not scalp it. A shorter lawn will allow the new seeds to make better contact with the soil. It is normal for the grass to turn a yellowish color after such a short mow, but rest assured that the new grass will improve its appearance in a few weeks.

Dethatching

The next step to consider is dethatching. A thick layer of thatch will not allow new grass seeds to reach the soil and germinate. If your yard has developed more than ½ inch of thatch, you will need to dethatch whether or not you plan to overseed. Any less than ½ inch of thatch will not be worth the stress on the grass. You can dethatch manually or with a machine. Dethatching has the tendency to pull up some healthy grass along with thatch, so be sure to time this step correctly with seeding.

Aerating

Lastly, consider aerating your lawn. While it is not essential for overseeding, doing so can aid the process, especially if your lawn is already quite thick or if your soil is compacted. Removing these small cores of soil will allow more air, water, and sunlight to reach your grass as well as give new grass seeds more places to grow. Like dethatching, you can aerate your soil manually or with a machine. Because the soil cores will break down naturally, you can leave them on top of the grass.

Sowing the Seeds

Once your lawn has been prepared, you can finally start sowing. This is the most simple part of the process. If you are only overseeding a small area, you may be able to do this by hand; however, if you are overseeding an entire lawn, you may find a seed spreader to be helpful. Spreaders will ensure more even coverage across your yard. To use one, simply fill it with the proper amount of seeds and walk across your lawn in rows.

What to Do After Overseeding

Taking care of your lawn after overseeding is key to its success. In order for the seeds to germinate, they will need to be kept moist but not over-soaked. Once the seeds sprout, they will not need as much water. Take extra precautions around these sprouts; too much water, sunlight, or heat will damage them and possibly leave them susceptible to certain root diseases. You will have to leave these vulnerable seedlings to grow for several weeks; do not mow, aerate, de-weed, or anything else that may disrupt growth. Make sure to also add a starting fertilizer as needed. You can also do this before you sow the grass seeds. Starting fertilizers are high in phosphorus, which is especially important for root growth. Taking these aftercare steps will ensure that your efforts yield a beautiful result.

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