Updated: Jul 13
Should I overseed my lawn? When is the best time to overseed? What type of seed should I buy? Is it better to aerate or verticut and overseed? How much should I water after overseeding?
Overseeding is one of the most important things you can do to help maintain a thick, healthy, durable lawn. There are many aspects that go into a proper overseeding to make sure it turns out successful and your resources are not wasted. In this post we will take you through the process of overseeding your lawn, from deciding if it needs to be seeded to caring for it afterwards.
Should I overseed my lawn?
Overseeding your lawn each year is always a good idea as it will introduce more disease resistant and heat & drought tolerant varieties of seed to your existing lawn.
However, if you want to conserve resources and only overseed as necessary, ask yourself the following questions before planning your seeding.
- Is my lawn thin or do I have any bare areas?
- Do I want to work in more seed of a specific variety?
- Do I have an abundance of shade that causes the lawn to thin out over time?
These are three of the main reasons why a lawn would need to be overseeded. If you answered yes to any of those questions, then an overseeding would be recommended.
Thin and bare lawns will be more vulnerable to weed issues as there is less competition to crowd them out. Thin and bare areas also retain less moisture and dry out quicker than a thick lawn as the sun is able to penetrate and warm the ground quicker. During the heat of summer this will cause cracks in the soil. Once the ground cracks, the pre-emergent barrier that was applied in the spring will be broken. This will allow unwanted grassy weeds such as crabgrass & foxtail to germinate and break through the surface.
A majority of new construction homes in our area are left with bluegrass sod. Bluegrass is a very high maintenance variety of grass as it takes twice as much water as fescue and is less heat tolerant. It is easy to see which lawns are bluegrass when the summer heat takes over. Working more fescue into these lawns is always recommended to create a nice mixture.
Cool-season grass such as fescue and bluegrass require about 4 hours of direct sunlight each day to thrive. If areas in your lawn receive an abundance of shade the turf will begin to slowly thin out. Replenishing shady areas each year is recommended to stay ahead of this.
When is the best time of year to overseed?
Now that you've decided to overseed your lawn, when should you do it? The best time of year to overseed in the Kansas City metro area is late summer to early fall, late August to mid October.
Why should you seed in the fall as opposed to the spring or summer?
Soil temperatures are elevated from the summer which will allow for quick seed germination.
Warm days and cool nights provide the perfect environment for your new grass to grow in.
The root system will have ample time to establish itself before the heat of next summer.
When seeding in the spring you delay the application of pre-emergents, which can lead to crabgrass or foxtail issues in your lawn later in the year.
Summer is never a good time to overseed as any air temperature over 90 degrees can easily zap a tiny seedling.
Spring seedings are only recommended for lawns with irrigation systems to allow for quicker germination or lawns with a lot of shade to limit grassy weed issues. Small bare areas in the lawn can be spot seeded in the spring as well. Topdressing bare areas with compost or topsoil is recommended in these spots.
Should I aerate or verticut and overseed?
Before deciding which method of overseeding to perform, it is important to take a step back and evaluate the current condition of the lawn. This will help you decide if an aeration and overseed, a verticut and overseed or both is best for your lawn. If you need some professional guidance, please feel free to reach out to us for a free lawn evaluation.
Verticut and Overseed
This method of seeding places small rows or slits in the ground 1/4 - 1/2 inch deep as if you were planting a crop in a field. This is the ideal depth for sowing grass seed.
A verticut and overseed is recommended for really thin or bare lawns as the seed will germinate throughout these rows creating a more uniform, even overseeding than an aeration alone. This method of overseeding is also recommended to incorporate more fescue into bluegrass lawns since fescue grows in a bunch formation and does not spread as bluegrass does. If only an aeration is performed it could lead to a "pot-marked" appearance in your bluegrass lawn.
The picture to the right displays a bare area after a month of growth that was verticut and overseeded. The grass will continue to grow and fill in creating a nice, even area of turf.
To prepare your lawn for a verticut and overseed it is recommended to dampen the soil by watering the lawn for a couple of days in a row prior to the scheduled overseeding, especially if it has been dry.
You will then want to drop your mowing height to around 2 - 2.5 inches and bag up the clippings. This will help reduce excess debris brought up by the verticut machine and help create better seed to soil contact, which is imperative for a successful overseeding. Finally, make sure to mark all sprinkler heads, shallow utility lines, electric pet fences and valve boxes with a flag so these do not get damaged by the verticut machine.
If you enlist Bison Lawns to assist you with your overseeding, we will always notify you at least 2 days prior to your scheduled seeding to give you ample time to prepare your lawn.
Aerate & Overseed
Most people are familiar with an aeration of the lawn as this is the machine that leaves the "dog-turd" like soil plugs behind. An aerator pulls soil plugs approximately 1/2 inch wide by 3 inches deep and deposits these, along with any thatch, on top of the lawn.
An aeration of the lawn provides many benefits such as alleviating soil compaction, reducing thatch build-up, encouraging healthy root development and improving watering & fertilizer efficiency. Given the importance of these benefits for your lawn, it is recommended to perform an aeration each year.
Lawns with only a few thin areas or ones that are already well established would benefit from an overseed with their aeration. However, it is important to know what variety of seed you are sowing and what type of grass you primarily have in your lawn before doing so. As discussed above, if your lawn is predominantly bluegrass and you are overseeding with fescue it could leave your lawn with an uneven, "pot-marked" appearance. A verticut and overseed would be recommended in this case.
The picture to the right displays a bare area after a full year of growth that was aerated and overseeded with fescue. As you can see, the seed only germinates and grows within the holes that were plugged. This picture also demonstrates how fescue grows in a clump instead of spreading as bluegrass does. In this instance a verticut and overseed should have been performed to fill in this area better.
To prepare your lawn for an aeration and overseed it is recommended to take the same steps as you would for a verticut and overseed.
For more information about the benefits of a lawn aeration, please read our Aerating Your Lawn post!
What type of seed should I purchase?
Selecting the right seed is just as important as choosing which method of overseeding to perform. It is very important to read the label on any seed you purchase to know what you are planting in your lawn. Seed purchased from big box stores can contain weed seed, crop seed and other varieties of grass seed that you DO NOT want in your lawn. Some of these grass seeds could be perennial grasses such as orchardgrass which would be difficult to get rid of once established.
For example, 1 lb of Turf Type Tall Fescue grass seed contains roughly 250,000 seeds and 1 lb of Kentucky Bluegrass contains over 1 million seeds! Purchasing the wrong bag of seed could potentially introduce thousands of unwanted seeds to your lawn. This is why it is imperative to make sure the label reads 0.00% weed seed and 0.00% crop seed. You can purchase high quality grass seed at local nurseries or landscape supply stores.
Bison Lawns uses only Blue-Tag certified seed that is guaranteed 0.00% weed seed and 0.00% crop seed.
How do I care for my new seed?
Once you have completed your lawn overseeding it will be important to maintain a proper watering schedule to ensure a high rate of seed germination and growth. Below is an outline of how to properly water and care for your new seed.
If you enlisted Bison Lawns to assist you with your lawn overseeding, we will provide you with proper watering and care instructions to follow after the seeding has been completed.
Watering Your New Seed
For lawns with the luxury of an irrigation system, keeping the seed bed moist will be as simple as adjusting your watering schedule. Below is a rough guideline for setting up your irrigation system for watering new seed. Times may need to be adjusted based on your individual lawn.
Follow the watering schedule below until the new seed has germinated, grown and been mowed twice:
- Set system to run everyday.
- Set system to turn on 2 - 3 times each day. 7 a.m., 10 a.m. & 2 p.m.
- Set rotary zones (sprinkler heads rotate around) to run for 5-7 mins.
- Set spray zones (sprinkler heads spray in one area constantly) for 1-2 mins.
- For non-irrigated lawns, place a sprinkler in an area for 10-15 mins twice a day as often as you can.
After your new grass has been mowed a couple of times you may adjust your watering schedule back to 3 deep waterings each week for the remainder of the season. This will help establish proper root development before the lawn goes into dormancy.
Mowing Your Lawn
Since you will be watering your lawn more than usual it will begin to grow rapidly. A lot of companies will tell homeowners to not mow until the new grass is ready to be cut. This could take 3 to 4 weeks! Delaying your mowing by 3 to 4 weeks will leave you with an overgrown lawn. Mowing an overgrown, wet lawn will leave behind clumps and excess grass clippings which will suffocate the tiny grass seedlings if they are left on the lawn.
Here at Bison Lawns we advise you to maintain your normal mowing schedule so long as you are mulching the lawn. This will not affect or harm any seed germination whatsoever. Increased mowing frequency of new grass seedlings will actually encourage growth.
Since the soil was disturbed during the verticut or aeration process and you are providing the soil with an abundance of water, not only will your grass seed germinate and grow but so will any weed seeds that were in the soil. You will want to wait until the new grass has been mowed twice before applying any herbicide to the weeds so you do not risk harming the tiny seedlings.
Fall leaves will also begin to become an issue. It will be important to mulch these up or remove them from your lawn as they fall so they do not suffocate the new seed. This will be especially important in shady areas. If you have trees on your property that drop leaves all winter, such as oak trees, raking these up would be recommended after you have put your mower away for the year. Any leaves left on the surface for a few weeks could cause these areas to thin out or become bare.