My Backyard: Overseeding in the Fall for a Better Lawn

Fall is the very important time to attend to your lawn. As I outlined in my post Fall Lawn Care Tips overseeding is important for your lawn.

There are two reasons to overseed in the fall.

1) Warm weather grasses which produce unappealing brown lawns during winter season. If you have a warm weather grass such as Bermuda grass, buffalo grass, zoysia or St. Augustine grass, you know that this grass goes dormant over the winter. Overseeding with a annual rye grass (Lolium multiflorum) which is a cool season grass will provide a green lawn during the winter. In addition it will die back once the hotter weather returns allowing your warm weather grass to take center stage.

2) Cool weather grass lawns with bare spots caused by the assault of summer temperatures.
If you have a cool weather grass such as Rye grass, Fescue, Bentgrasses and Bluegrass, you know that this grass really prefers the cool temperatures of fall and spring. Therefore often by the end of the summer your lawn has taken a beating and you may find bare spots in your lawn. Overseeding will sow seed over your existing lawn in order to fill in those bare spots.

As you see overseeding your lawn have different purposes in depending on whether you have a cool or warm weather grass lawn. Nonetheless the overseeding is performed in the same manner.

5 Steps to Follow when Overseeding

1) Prepare your lawn:

Since these seeds will be competing with your existing lawn for light. You need to get it as much light as possible. This is done by cutting your lawn to a height of 1.5-2.0 inches.(normally lawns are cut to height of 3.0 to 3.5 inches)
Make sure to rake and bag all clippings so your seed has a good chance of making contact with soil. I have a mulching mower and normally do not do this but do it when preparing for overseeding.
Dethatching is done every two to three years. If it is that time for your lawn make sure that is done first.
It is best if you perform a core aeration on your lawn. This will reduce the chance of thatch getting in the way of your seed getting into the soil. Core aerators (or "lawn aerators") can be rented from local rental centers.
In severe cases, you may need to add a layer of topsoil before overseeding lawns. For instance, due to shallow tree roots popping up on the lawn, your topsoil layer may be too thin. Spread 1/4" of screened topsoil over such an area, and rake it in.

2)Choosing the seed to use and determining how much to buy.

Buy the highest quality that you can find on the shelf. While it will be a bit more expensive than the others, you are getting the most recent technology in breeding for disease resistance and appearance for your money.
When overseeding your warm weather grass you need to use annual rye grass (Lolium multiflorum)
When overseeding your cool weather grasses it is a good idea to use a blend of perennial cool weather grasses. Kentucky blue grass being the most popular.
Bags of seed have information on the back regarding BOTH recommended seeding rates and overseeding rates. Because you do not always have the luxury of time to water and care for newly sown seed that turf professionals have, the germination rate is likely to be lower. Using more seed than necessary compensates for some of the loss. So follow the seeding rates when calculating how much seed to buy.
Do not forget to know the square footage of your lawn also.

3) Sow Grass Seed

Use a spreader. I use the “rotary” type of spreader because it avoids missing spots in the lawn. The “drop” spreader is a bit more accurate in terms of knowing where your fertilizer or grass seed is going but the rate the seed is released is more difficult to control.
When using a seeding device, divide the total amount of seed in half. Spread the entire area to be overseeded with the first half, and then go over it again in a different direction with the second half of the seed. That reduces the chances of missing any spots in the lawn.

If you are using Kentucky bluegrass, which is a very small, light seed, borrow a trick from turf professionals. Give the seed some heft by mixing it with another material, or "carrier," such as sawdust, sand, or fine vermiculite.

lightly rake over the lawn surface to bring the seed into contact with the top 1/8 inch of soil.

Use a garden rake it will take more time, but it gives seed better soil contact than a grass or leaf rake.

You may want to take an extra step and topdress the overseeded lawn with a thin layer(no more than ¼ inch) of organic material such as topsoil, compost, or peat moss. Will protect the new seed and help keep it moist. This is completely optional!! If you do not top dress it just means you need to water more often

4) Watering Your Lawn after Seeding

Grass seeds must be watered properly, in order to germinate.
Use just a fine spray. The soil should be kept evenly moist, puddles should not form
You may need several waterings per day (depending on the weather), for several weeks. Proper watering is so very important. Often people don't stay attentive to this detail and then wonder why grass does not grow!
After the grass blades sprout, you'll still need to water a couple of times per day
You should gradually decrease watering to once a week. How you know if your grass needs water is to push the blades down and if they don't spring back up quickly, they need water.

5) Final tips

Lawn mowing can begin again once the seedlings reach 3 inches tall.
Five weeks after the grass has sprouted, apply a quick-release nitrogen fertilizer at the recommended rate; repeat in another six weeks.
Annual rye grass will die in the summer, conveniently making way for warm-season grasses to take over, the annual rye grass will still, nonetheless, be around in spring, offering unwanted competition with warm-season grasses. One way to minimize this competition is to mow the annual rye grass as low as possible in spring. By keeping it short, you'll at least minimize the amount of sunlight that the annual rye grass robs from your main lawn, which is now emerging out of dormancy.