By Donna Dolinar, Wyandotte County Extension Master Gardener since 2006
If your otherwise lovely lawn is marred by patches of thin or bare spots, it would seem you are due for some overseeding. Overseeding is when you plant grass seed in an already established lawn.
Don’t just throw some seed in the area, walk away and expect the area to fill in. It will take just a bit of work, but not much. First you need to prepare the soil.
Aerating is one choice. To aerate the ground you need to poke holes in it. This can be done in several ways, including using an aerator machine that pulls plugs of soil to allow air to penetrate below the surface. Aerating is not your only choice, especially if you only have a few spots to handle. You do, however, need to prepare the soil.
Mow – Be sure the surrounding grass has been mown to an appropriate length, usually around 2 inches. That will give you better access to the spots you need to treat.
Clean – Clear the area by removing any debris including sticks and rocks. Dispose of these items appropriately. Leaving them around won’t do the rest of the grass any good.
Dethatch – Thatch is that layer of grass clippings that have accumulated between the ground and the grass blades. Note: A certain amount of thatch is good for the lawn, but too much is going to impede a lush ground cover. But, back to the issue at hand. In the area you want to seed, remove any thatch and add it to your compost pile. Thatch removal can be handled with a good rake. Be sure to use a sturdy, lawn rake and not a lighter weight leaf rake. If you are working with a larger area, you may want to consider using a dethatcher.
Rake the Soil – Now that the area is clear, use that same rake to break up the surface of the soil. Much like aeration, this will give the seed some place to sit, germinate and take root.
Sow the Seed – Use fresh seed. Use the same variety or combination that you already have growing in the lawn. If you used an herbicide recently to kill weeds, check the label on that herbicide to see how soon you can reseed after its use. The time frame varies by type of chemical and the amount or strength of herbicide applied. If you have several or larger areas to cover, use a broadcast or drop spreader. For very small areas, you can hand toss. Don’t seed on a windy day or your seed will go flying into a neighbor’s yard or into the street.
Watering – There will be a great temptation to just let Mother Nature do the watering. If you are positive that the rain will only be a light shower, then things are fine. But if you have just seeded and you get a strong rainstorm before the seed has had time to germinate, all that seed will go sliding down the street into the storm drain. The best choice is to gently water the place(s) you seed twice a day. Once you see the little grass bits start to poke up, you can ease off. This will take about two weeks, possibly three. Too much or too strong watering will just drown your hard work.
Mowing – Keep the rest of the lawn mowed on the short side. That will give your new grass a chance for sun.
Feed – Fertilize the entire lawn about six weeks later using nitrogen.
Stay Off The Grass – While your seed is trying to germinate and grow, do your best to keep from walking over the area or allowing pets or children to play in the area. Constant traffic will only impede your progress.
Timing is Everything – Spring may seem like the time to get this job done. However, that is also the time that most weeds are popping up. There is no reason to give your new grass any more competition than necessary. If you wait too long in the spring, you risk the weather becoming hot and dry. This will be fine if you want to feed the birds, but not good for filling in bare spots. Seeding in the summer only stresses the lawn more. So, autumn is probably a good choice. Select early fall so that the grass will have enough time to establish itself before the cold and wet winter sets in.