What You Need to Know 
 

The best defense is to keep your lawn healthy by fertilizing and topdressing with organic material once a year. Mow your lawn correctly and aerate it periodically to discourage thatch buildup and soil compaction.

Even with the best care, bare, thin, or weedy patches occasionally develop in certain areas. Deal with these problems as soon as possible so the damage doesn't spread. Weeds rapidly will fill in bare areas if you don't populate that space promptly with new grass.

Repairing a lawn problem is a two-step process. First, try to determine the underlying cause. Sometimes an accident, such as a fertilizer spill, creates a bare spot in the lawn. Or the cause might be chronic disease, destructive insects, or competition for light and moisture from overgrown neighboring plants. Correct these deficiencies first, or your repair efforts will be futile.

Give a thin, tired lawn new vitality and disease resistance by overseeding it with new grass seed. In northern states, do this in the fall, so the cool-season grasses have time to develop strong roots before they have to face summer. In southern states, repair lawns of warm-weather grasses in the spring by sprigging or plugging -- these grasses need warm weather to grow well.