An acceptable quality lawn is the goal of many homeowners. With proper establishment and care, this goal can be achieved. Unfortunately, situations may occur that lead to a thin, damaged, or dead lawn in need of repair or renovation.
Determining the cause of the lawn decline is the first step in the lawn renovation process. Many lawn problems originate from poor soil conditions.
Heavy clay, compacted soils, and poorly drained soils may be the reason a lawn is doing poorly. These situations can be corrected during renovation. Other lawn problems tend to be due to pests, weather conditions, or poor lawn care practices. Perhaps implementing proper mowing, fertilizing, and watering may be all that's required to achieve acceptable lawn quality.
Once the problem has been identified, the renovation process may begin. Think of renovation as fitting one of three levels: overseeding with little additional work; significant work, but allowing existing grass to remain; or completely removing the existing lawn and starting over. The decision of which level to choose is based on how bad the lawn looks and what caused the problem.
For example, if the lawn is just a little thin and the soil structure is good, overseeding with a quality lawn seed in late August or early September may be the answer. Use a slit-seeder, which is a specialized machine that will cut slits into existing grass and then drops seed into those slits. It is an ideal way to overseed lawns. Seed may also be broadcast over thin lawn areas, but there needs to be good soil-to-seed contact.
Dethatchers or vertical mowers can also be used to remove excess debris prior to overseeding. In addition, slit-seeding could be done directly through grass and/or weeds killed with the nonselective herbicide glyphosate. All of these types of overseeding procedures do not require additional soil modification.
When soil problems exist under a lawn, there are ways to address them without tearing up the lawn. Core aerifying is suggested for problems such as thatch and soil compaction. Core aerifying machines will pull up numerous plugs of soil about the diameter of a pencil, making holes in the lawn. Allow the plugs to remain on the soil surface. Aerifying, overseeding, and slit-seeding (breaks up cores) may be an ideal level of renovation for many lawns. When soil problems exist, organic matter used as a topdressing can begin to rebuild soil structure. This becomes an important part of the reseeding process. In these situations, core aeration should be done first, topdressing second. This allows organic matter direct access into the soil profile.
Unfortunately, some lawn problems, such as soil problems of severe compaction, high clay levels, or poor drainage, require starting over. To do this, remove existing grass or rototil it into the soil. You will want to introduce organic matter into the heavy soils.
High populations of perennial weeds may require the use of a nonselective herbicide such as glyphosate or persistent working of the soil until you are sure weeds are no longer going to be a problem. Thoroughly work the soil to a depth of six inches. This depth may not be possible if you have shade trees in the area. You should not disturb the root system. In these cases, lightly working the soil enough to sow the seed and using an organic matter as topdressing is the best you can do. Add amendments such as compost, rotted manure, organic topsoil, or peat, and thoroughly work into the soil profile. Follow proper selection and establishment procedures to get the new lawn off to a good start.
From Lawn Talk: