Battling weeds and bare spots in your cool-season lawn? September is the perfect time to help your lawn thrive.

Area lawns flourished with rainy, cooler weather in late July. Early summer heat and drought had taken their toll, but seemingly overnight, brown lawns sprung back to life.

The weeks before fall arrives are an excellent time to assess your lawn. September is the most important month of the year to fertilizer and seed for another season.

Is your lawn thin or patchy?

If you have a thin stand of grass, early September is the optimal time to overseed. Sunny days combined with cooler nights and warm soils offer the perfect combination to ensure grass quickly germinates and establishes. Start planning now so you don’t miss the ideal window for seeding.

Overseeding is best accomplished by verticutting. A verticutter is a machine that is larger and heavier than a lawn mower.

As the machine moves through the lawn, a row of spinning blades cut through the sod layer to create grooves in the soil. Once the seed is spread, it moves into these shallow grooves providing necessary seed-to-soil contact and leading to better germination.

Rent a verticutter from a local hardware and rental store. Plan ahead as the number of machines is limited. During the busy season, you could miss out on getting the seed down.

Keep in mind, seeding is only for bare patches and thin, sparse stands. If you have a good stand of grass, there is no need to add more seed.

Is your lawn hungry?

Summer sun, growth and rainfall have left the turf in need of additional nutrients. Cool-season grasses, like tall fescue and bluegrass, naturally go into dormancy over the summer. The cooler September days awaken the grass.

September fertilization can be compared to breakfast, the most important meal of the day. This timely application feeds the grass when it naturally wants to grow.

September also is the time for rapid growth in turf. Grass develops new roots, crowns and top growth, resulting in a thicker stand of grass. It is this thick stand we need to help choke out weeds.

Nitrogen, the first number on a bag of fertilizer, is the most critical nutrient. Nitrogen drives the processes. Local soils tend to be naturally high in phosphorus and potassium, the other nutrients needed.

Early September is the ideal time to apply a high-nitrogen fertilizer. Look for a bag with the first number around 30% nitrogen and the next two numbers, phosphorus and potassium, as close to zero as possible.

Even low maintenance, cool-season lawns benefit from fertilizer.

The exception to this recommendation will be for lawns that have had a soil test that indicated the need for additional phosphorus and potassium, or if you are overseeding. A starter-type fertilizer would be recommended in these situations.

Don’t miss this window of opportunity to prepare the lawn for next season. By planning now, you will work with the grass on the battle against weeds and bare spots.

Nelson is Oklahoma Cooperative Extension Service ag educator for Garfield County.

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