MSU Extension

The summer of 2012 is gone. The air is getting cooler, days shorter and gardening activities are winding down. There are some projects that still need to be done. Some people have noticed that their lawns are looking a bit thinner due to a summer of drought. If there are many large, dead patches in your turf or weeds make up 40 percent or more of the lawn area, it’s time to do something.

In Michigan, mid-August through September is the ideal time to repair or seed a new lawn, but if the weather is favorable, it may be possible to seed into early October and still achieve good establishment. It is more risky to start in October because you never know what the weather is going to do. If it stays warm through the month, newly seeded grass will have some time to become established. If it get cold too soon, the seed may germinate, but the plants may not have enough time to become established.

One option for this time of year is to overseed directly into the existing turf. As the new grass grows in, there will be less room available for weed seeds such as crabgrass to germinate next spring and become established. In my opinion, the best way to accomplish this goal is to use an overseeder, or a slit seeder. This machine, which is about the size of a push lawn mower, will slice grooves in the turf and will place the seed in the grooves, resulting in good seed-to-soil contact. This method requires no soil preparation and provides good results if cared for properly.

After overseeding, do not use any broadleaf weed herbicides until the new grass is up and established. This takes about two months, so there will be no time for treatment this fall. If rainfall is not sufficient, water once or twice a week for 15 to 20 minutes to keep the seedbed moist. Add some nitrogen to the soil such as 10 lbs/1,000 sq. ft. 10-10-10 or 12-12-12 to get the grass off to a good start. Ideally, a soil test should be run before starting the project for more accurate fertilizer recommendations. The fertilizer can be added before or after overseeding. If possible, select a mix with a slow release formulation of nitrogen.

Most northern lawns in our area are composed of a mixture of Kentucky bluegrasses, fescues and perennial ryes. Having a diversity of species is better for disease resistance and adaptability to a wide range of light and soil conditions, but you are not limited to what is available in packaged products. I like to buy mixtures, but I generally purchase additional Kentucky bluegrasses separately and add them to my mix because I like the look of Kentucky bluegrass.

Whatever you decide to do, keep a record of what you plant. In the event you need to patch some areas later, there will be a record of the species mix. This will help to avoid patches of various shades of green in the lawn. In Michigan, the recommended seeding rate is 3 to 5 lbs/1,000 sq ft. I prefer to use the higher rate. Since this is a long-term investment, I don’t like to cut corners. Start by seeding in one direction such as north to south. If there is seed left over, repeat the process going east to west. Any remaining can be sown in a diagonal direction. The goal is to place enough seed down to produce a lush lawn. If there is mole activity in the lawn, roll it before seeding. The overseeder will bog down in soft soil. It is best to get rid of the mole by trapping, but you decide. (See Moles in the lawn for more information on mole trapping.)

Another option is to try a dormant seeding. This where the seed is sown after temperatures have fallen below the germination temperature, usually in November. The advantage here is that the seed will be in place and ready to grow as soon as spring conditions permit. The goal is to have the grass seedlings compete with the germinating weed seed. If an overseeder is used, there is less concern about seed washing down to low areas, but there is a greater chance of loss due to rotting or consumption by insects such as grubs.

Additional information:

• MSU Extension's Drought Resources