Early September is the perfect time of year to fill in bare spots or dead patches in your lawn, because soil temperatures are high, nighttime temperatures start to cool off and (hopefully) more rain begins to fall.
First, core aerate and/or verticut to break up soil. Verticutting slices grooves in the soil, creating an area for seed to fall. This method is preferred for overseeding. Mow the grass short (1 to 1.5 inches), then verticut in one or two directions.
High quality seed is a must. Avoid inexpensive seed such as creeping red fescue, fine leaf fescue, perennial, annual rye and annual bluegrass; they are sure to fail under stressful summer conditions.
Check the seed label to ensure you are getting good varieties of bluegrass or tall fescue. No other species will tolerate our local conditions.
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New seedlings need fertilizer to help them establish and develop quickly. New seed should be fertilized with a balanced product such as 13-13-13 or a high phosphorus product such as 10-20-10. Fertilizer should be applied at the rate suggested by a soil test (available through your Cooperative Extension office) or a starter fertilizer should be used at the rate suggested on the bag.
About four weeks after germination, apply a high nitrogen fertilizer such as 27-3-3 or 30-0-0 at labeled rates. This application should be repeated in mid-November to send the grass into winter, strong.
Seed should be applied at half the rate that is used for new lawns on bare soil. For tall fescue, the overseeding rate is 3 to 4 pounds per 1,000 square feet. The overseeding rate for bluegrass is around 2 pounds. Fescue should germinate in about 10 days; bluegrass may take up to two weeks.
Keep the seedbed moist to ensure rapid germination.
The ideal window to overseed is very short. Plant your seed by Sept. 20.
Dennis Patton, horticulture agent with the Johnson County office of the Kansas State Extension Service. To read more on this or other topics or to get answers to your gardening questions, go to KCGardens.KansasCity.com.