Answer: Either fall or spring are excellent times to renovate and repair existing lawns. 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. On the other hand, many 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, overseeding with a quality lawn seed in late September may be the answer. Seed may 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 tear out 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 into 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.
Unfortunately, some lawn problems, such as soil problems of severe compaction, high clay levels, or poor drainage, require starting over. Remove existing grass or rototil it. High populations of perennial weed species may require use of a nonselective herbicide, such as glyphosate. Thoroughly work the soil to a depth of 6 inches. Add amendments such as compost, rotted manure, organic topsoil, peat, etc. Then overseed the area, water well, and fertilize lightly. (Use a 3-1-2 ratio of nitrogen, phosphorous and potassium).
Best wishes with your new lawn!
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