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Johnson County
11811 S. Sunset Drive
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Olathe, KS 66061

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Seeding Cool Season Lawns: Early September is best

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Overseeding the lawn is usually an annual September project. However, if it’s been a “best ever” summer in the Kansas City, fewer people rush to the garden center in the fall to purchase grass seed. When mild temperatures and timely rainfall have resulted in a green summer and the making of a great fall, overseeding is not foremost on peoples’ minds.

However, even after the best of summers, not all lawns escape the need for overseeding. The best time to plant new tall fescue and bluegrass seed is in early to mid September.

The best window for seeding a Kansas City lawn
Although September is the best time to seed, often conditions are right for planting grass seed up to October 15 with good results. The problem with late-season seeding is that Mother Nature sometimes works against ensuring the production of a new stand of grass by winter. Shorter days and cooler temperatures prolong the germination of the seed and its establishment.

Establishment of the tender grass is a must for it to survive the winter. Grass that is seeded late can die as a result of the cold, harsh conditions, or due to drying out. Freezing and thawing of the soil, coupled with a lack of moisture, leave the tender roots and crowns susceptible to desiccation.

Seeding late into the season requires the same steps as earlier planting. Proper soil preparation is a must. This is best accomplished by either verticutting the lawn or through core aeration. These machines open up the soil surface and allow the seed to come in contact with the soil.

Irrigation for good seed germination
Timely and proper irrigation are also crucial. Once the seed is sown, the upper surface of the soil should remain damp at all times. This may require daily, light watering, depending upon the amount of sunlight and wind. It is necessary to be prepared to water when needed because inadequate water will slow establishment.

Use a seed starter fertilizer
An application of fertilizer at the time of seeding is also recommended. This will help nourish not only the new seedlings, but will give the existing turf a much needed boost. Providing the new, establishing grass with ample nutrients will also help speed up the growth process and increase winter hardiness.

Once the grass is up then mow
Lawns should be mowed at the normal height, between 2 and 3 inches. The mistake of letting the new grass grown too tall reduces the seedlings’ ability to develop a strong crown. Clippings may be left when mowing provided they do not shade out the new seed. Fallen leaves should be picked up to prevent suffocation.

Weed control at this time is not an issue because no chemical applications can be safely made while the grass seedlings are becoming established. As a general rule of thumb, herbicides should not be applied until the new grass has been mowed at least twice. Check the product label for specific information.

Late season seeding can still be done, but there is no time to waste. Seeding today is better than waiting until tomorrow. By following a few simple steps, and with the cooperation of Mother Nature, lawns should be in tip-top shape next summer.

Other Resources

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Have questions? The Garden Hotline is staffed by trained EMG volunteers and Extension staff who will assist you with questions.

Phone: (913) 715-7050

Email: garden.help@jocogov.org