Hard to believe it is quickly approaching the time to seed a new lawn or over seed what is there. Our best window of opportunity to ensure a good stand that will survive winter is August 15 through the first week in September.
Full sun exposure will do best with a blend of several disease resistant Kentucky bluegrass cultivars. New lawns will use about 1.25 to 1.5 pounds of seed per 1,000 square feet. Over seeding into an existing full sun lawn will take about one-half that rate.
For a new seeding, soil preparation is everything. This is your one chance to get the lawn off to a great start. Adding a quality compost or other forms of decomposed organic matter will aid in soil moisture retention, create soil air spaces, improves soil structure, and as it continues to break down, release nutrition into the soil profile to the benefit of grass. All forms of organic matter contain carbon, a very necessary building block for our soil microflora that work together with the grass root systems, each giving the other something they need for good growth. If you have the results of a soil test, this is a great time to apply either synthetic or organic levels of nutrition. Much easier to do now especially if a large amount needs to be used. Loosening the soil and incorporating the organic matter several inches (6-8 inches, or as as deep as reasonable) will provide an ideal seedbed.
Time to seed now once all the rest has been done. Fore best coverage, cut the seeding rate in half and sow the seed in two directions. This will help with any “operator error” and “spreader” issues. Grass seed and specifically Kentucky blue grass seed is quite small and only requires a very light raking to get it into good soil seed contact. One way is to use a leaf rake turned upside down. The goal is to get the seed covered, but not moved around.
If you are over seeding, there is still some preparation that can be done ahead of the seeding. Core aerification relieves soil compaction; helps manage thatch and the core that ends up on the surface acts as a mini top dress as it breaks apart. For the machine to work properly, the soil needs to be moist, so plan to water the lawn very well a day or two before hand or if you are lucky get it done right after we have some rain. The coring will take a plug out 3-4 deep so getting the soil moist that deep is the goal. 1” of water per 1000 square feet of yard requires 620 gallons of water. Thin spots, low spots, bare spots can also be top-dressed to assist in recovery before you re-seed. Buffing the seed down to the soil is also a good idea using that same leaf rake.
To get your seed going, watering is critical. On the new lawn, constant moisture is key so once you start you cannot stop. Manage the watering based on the weather conditions and if we get any natural rain. Light frequent watering is better that a soaking that leaves standing water. Grass seed rots very easily. Continue to water, modify as needed, and mow the lawn as soon as it needs it. Be sure your mower blade is sharp as the young seed is tender and can literally be pulled out of the soil or otherwise damaged.