Certain aspects of lawn care are most effective when performed in the fall:
Fertilize. Don’t wait until spring. Feed the lawn in the fall. This helps build strong, deep roots, which translates to greener, healthier grass next year. Fertilizer applied in the spring feeds weeds and makes you have to mow more often. Use a slow-release fertilizer high in nitrogen (the first number in a ratio such as 21-7-14). Follow package directions. Follow up with a “winterizing” fertilizer in late fall.
De-thatch. Lift a small patch of lawn from a depth of 3 or 4 inches. A thick tangle of dark brown roots and stems at the soil level signifies thatch, which chokes growth. If the thatch is more than a half inch, aerate the lawn. If it is more than three-quarters of an inch, aerate and then apply a thin layer of soil of compost, which introduces microorganisms that break thatch down.
Seed. Till the soil to 6 inches, mixing in compost as you go. Smooth the surface and apply starter fertilizer. Spread the seed and keep it well watered as the grass sprouts and gets established.
Weed control. Whether you hand-pull weeds or spot-treat them with herbicides, fall is a good time to get them under control. The actively growing lawn will quickly fill in the spots where the weeds were.