Here's a rundown of fall tasks that will improve a lawn made up of cool-season turfgrasses, such as fescues, Kentucky bluegrass and ryegrass:
Aerate. Before overseeding or feeding the lawn, aerate it. A core aerator machine will pull plugs of soil out of the lawn, allowing seed and fertilizer to make better contact with the soil and to obtain a more even distribution.
Fertilize. Apply a slow-release nitrogen-rich lawn fertilizer in early fall, following package directions.
Overseed. Spread fresh seed over sparse or worn areas. Water the seeds lightly but frequently until they sprout, and continue watering until the new grass is about two inches tall. Begin to ease up on the watering to promote a deep root system. Mow the lawn once it is three to four inches tall, removing no more than a third of its height.
Mow low. It's best to mow grass on the high side during the growing season, to help it conserve water and shade out weeds. However the last mowing in fall should be short—to one inch—to help avoid winter damage and disease.
Mulch fallen leaves. As deciduous leaves fall on your lawn, run over them with the lawn mower. The chopped up leaves will decompose fairly quickly and replenish nitrogen in your lawn's soil.
Know what to do and when to do it with Taunton's Lawn Guide.