We usually don’t see a lot of rain during a Kansas City summer. This year has been one for the history books: There have been a few weeks of heat but seldom have we been dry. As a result, lawns have fared nicely. September is one of the most important periods for caring for the lawn. It is the ideal time to overseed for a healthier turf.
Warm soils, sunny days and cooler nights of fall make it the perfect time to plant cool season bluegrass and tall fescue grass. Early September’s weather provides excellent conditions for the grasses to establish successfully. Spring seeding is not advised because of the stresses from hot and dry weather, which means the grass rarely survives the summer.
In addition to the proper timing, successful seeding requires two key factors; good seed-to-soil contact and ample water.
Like all seeds, they need to be covered with soil to provide germination. Grass seed is small and does not need to be covered deeply. But the hard soil crust must be broken and loosened. Simply throwing seed on bare soil will not work.
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Small patches can be raked vigorously to break the upper quarter- to half-inch crust. Larger patches or sections of the lawn can be prepared with a machine called a verticutter or slice seeder. This machine is basically a spinning bar with closely spaced blades that cut through the soil surface, breaking the crust.
The soil should be moist when running a verticutter. Mow the grass short prior to verticutting and remove the excess clippings. Making two passes with the machine in opposite directions loosens more soil for better seed-to-soil contact. The grass seed can then be broadcast over the area, moving into the grooves that were cut into the soil by the verticutter. Gravity, water or even a quick third verticutter pass will cover the seed. An application of a starter fertilizer is beneficial to provide quick establishment.
The other key to overseeding is proper watering. It will take one to two weeks for the seed to germinate, and the tender seed must be kept moist or damp through this entire time. There is not a set schedule for how often or how much to water.
Watering depends greatly on fall weather patterns. Sunny, windy days will require more frequent watering than cloudy days. The key is to apply enough water to keep the upper surface damp at all times. With the rain over the last month there is good subsoil moisture, so replacing water lost to surface evaporation is key. As the grass germinates and establishes, the light, frequent watering applications can transition into deeper and fewer applications.
Dennis Patton is a horticulture agent with Kansas State University Research and Extension. Got a question for him or other university extension experts? Email them to firstname.lastname@example.org or visit KCGardens.KansasCity.com.