Research has shown that an attractive, well-kept lawn improves the appearance and increases the value of a home. (Credit: Pixabay)

For seeding or overseeding a lawn, September has long been considered the best month. This is true when cool season grass species such as bluegrass and fescue are being used. At this time of the year, soil usually is not excessively wet and works well. Additionally, fall rains are soon to come to make watering, which is necessary for good seed germination, less of a chore. In fall, some of the problem weeds such as crabgrass do not germinate and crowd out young, tender turfgrass seedlings as they do in spring.

In preparing for seeding a lawn, one of the first steps is the elimination of existing perennial vegetation. This often means the application of a non-selective herbicide such as glyphosate to kill problem grasses such as Bermudagrass as well as most broad-leaved weeds. It normally requires at least two weeks after the application of a herbicide before the area can be worked, but there still will be time to prepare and seed the area. If the fertility level of the soil to be seeded is not known, a soil test would be helpful, particularly for the establishment of a new lawn.

Eliminating existing vegetation through the use of a non-selective herbicide such as glyphosate is recommended for renovating existing lawns. (Credit: Penn State University)

If weather conditions have been dry, it is beneficial to water the area to be seeded several days before preparing the seedbed. A slightly moist soil will form a better seedbed than dry soil. After the soil has been moistened and weeds are yellow and dying, the soil should be tilled to break up compaction and aerate the soil. It also is a good time to incorporate lime and fertilizer, according to soil test recommendations. If the area to be seeded has a layer of dead thatch, this layer either should be removed or tilled deeply into the soil. If the soil is low in organic matter, the incorporation of compost, peat moss, well-decomposed manure or other similar materials can speed the establishment and growth of the newly seeded area.

If the area to be seeded contains a layer of thatch, it should be removed before seeding. (Credit: Adobestock Images)

The pH of the soil is best determined by a soil test and should be adjusted so that the acidity of the soil is between a pH reading of 6.0 to 6.5, for best grass growth. Lime is used to raise soil pH, while sulfur is used to lower it. The latter is rare for most Missouri soils. Ground limestone used for raising pH and is readily available at many retail outlets. It is slow to react and should be incorporated into the soil before seeding. If it must be applied to an existing lawn, it will be most effective if it is worked into the soil after it has been spread on the soil by using specialized equipment such as a vertical mower or power rake.

If it is not possible to have soil tested before seeding, a few general recommendations might be followed. If the soil has been limed in the past but not for at least two years, apply about 25 pounds of ground limestone per 1,000 square feet of lawn area. Phosphorous will also most likely be needed. Add it to the soil at the rate of 5 to 7 pounds of treble superphosphate (0-46-0) per 1,000 square feet. Since phosphorous and lime are not very mobile in the soil, till in both to a depth of at least 4 to 6 inches. To supply a little nitrogen and potassium to serve as a starter, in the final preparation of the lawn for seeding, add a complete fertilizer such as 10-10-10 at the rate of about 10 pounds per 1,000 square feet and work it into the top inch of soil. Nitrogen and potassium are very mobile, so more can be added later as a lawn fertilizer after the grass has germinated and reached the height when it first needs to be mowed.

The seedbed should be fairly fine and free of large clumps of soil. Additionally, make it as level as possible. High areas may dry too rapidly, and grass seeds may die during germination. Low spots often remain too wet, particularly if frequent rains develop during the germination period, which would lead to reduced germination.

A slit seeder is a specialized piece of equipment for overseeding established lawns that negates the need for seedbed preparation. (Credit: Juan Rodriguez)

There are many good turfgrass varieties available. Kentucky bluegrass remains the standard for aesthetic merit by which other cool season grasses are judged. However, the fine-bladed, turf-type fescue varieties are becoming very popular and have good durability and disease resistance. Once the area is ready to be seeded, bluegrass should be spread at about 2 to 3 pounds per 1,000 square feet whereas fescue will require 6 to 8 pounds per 1,000 square feet. After spreading the seeds, aged straw or hay that is free of weed seeds can be used as a mulch. The purpose of the mulch is to help retain seedbed moisture and provide some protection from newly germinated grass from the elements. Do not spread the mulch too thickly. One bale of straw should be enough to cover 1.000 square feet. There is no need to remove the mulch after the grass seeds have germinated.

From the standpoint of appearance, Kentucky bluegrass remains the standard of excellence for cool-season turfgrass species.) (Credit: Wikilawn.com)

Keep the surface of the seedbed moist during the germination process. With proper care, fescue varieties should germinate in about a week to 10 days and bluegrass in 2 weeks or a bit more. Once germination is complete, reduce watering to about once per week or enough so that with natural rainfall seedlings will be provided with about an inch of water per week. More details for lawn establishment and renovation are available from MU Extension guide 6700, entitled ‘Cool Season Grasses: Establishment and Renovation ’ which can be found at https://extension.missouri.edu/publications/g6700.