Now is the perfect time to overseed any bare spots in the lawn. Warm soil temperatures combined with cool air temperatures lead to quick germination and establishment of seeds. Soil preparation, seed selection, fertilization and irrigation are key for success.
Start by mowing the grass short (1 to 1.5 inches) and then verticut in one or two directions. Verticutting slices grooves in the soil, creating soil contact for the seed. Remove debris from the lawn to achieve the needed seed-to-soil contact.
High-quality seed is a must. Avoid inexpensive seed containing creeping red fescue, fine leaf fescue, perennial, annual rye and annual bluegrass. These species may look good quickly after seeding, but they fail under stressful weather. Check the seed label to ensure you are purchasing bluegrass or tall fescue. No other grass or other crop species can tolerate our local conditions.
A starter fertilizer helps seedlings to establish and quickly develop. Existing grass also benefits from this application. Unlike the standard grass fertilizer that is high in nitrogen, new seed requires a balanced fertilizer such as 13-13-13 or a high phosphorus product such as 10-20-10. Phosphorus is a macronutrient that aids in root development.
In my experience, I find people do not apply enough fertilizer when seeding. They are afraid of burning the new grass. In fact, the opposite happens. Because of the lack of nutrition, the seedlings fail to grow. Apply a high nitrogen fertilizer such as 29-0-4 or 30-0-3 about four weeks after germination. Repeat this application in mid-November to send the grass into winter adequately fed. The result will be an early spring green of the lawn without the excessive mowing.
Frequently a lawn is thin and needs additional grass to thicken up. Determining the correct rate of seeding is important. Seed is usually applied at about half the seeding rate that is used for new lawns on bare soil. For tall fescue, the rate is 6 to 8 pounds per 1,000 square feet. The overseeding rate is 3 to 4 pounds per 1,000 square feet. The new lawn rate for bluegrass is 3 to 4 pounds per 1,000 square feet, which makes the overseeding rate around 2 pounds.
Adjust the seeding rates up or down based on the current stand of grass in your lawn. Fescue should germinate in about 10 days while bluegrass may take up to two weeks.
Once the seed is sown, germination is dependent on water. The seedbed must be constantly moist to ensure even germination. This requires frequent, light irrigation to keep the upper surface moist at all times. The watering schedule can become progressively deeper and less frequent as the seedlings establish.
Remember, the ideal window to overseed is very short. The greatest success is achieved by having the seed planted by Sept. 20. Take advantage of these favorable conditions for establishment and follow these helpful hints for success.
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.