University of Illinois Extension

Fall Lawn Care

"Managing your lawn in the fall will ensure a fuller, greener lawn next spring. Taking care of your lawn this fall really depends on the kind of summer temperatures and the amount of rainfall you have had,” said Richard Hentschel, a University of Illinois Extension specialist.

“In parts of Illinois where rainfall has been plentiful, homeowners have had to mow more often than expected to keep up with the rapid growth and maintain the one-third rule of removing no more than one-third of the grass at a mowing.”

If you have had that amount of rain along with high temperatures, turf grass diseases have been a problem and may have left your lawn thinner than you’d like, he added. If rainfall has not been plentiful, your lawn may be thinned due to drought.

“You may need to over-seed thinned areas or re-seed bare areas of your lawn and fall is a great time to do that,” he said. “Since most weed seeds tend to germinate in the spring of the year, you get a much better stand of new grass in the fall. Whatever method you use, be sure to purchase high-quality disease-resistant seed.”

Prior to seeding, lightly top-dressing the area is recommended. Top-dressing serves two purposes. First, it provides a seedbed for the new turf seed and, second, it fills in those low spots that held extra soil moisture which likely contributed to lawn diseases.

“Timing is also important to allow for adequate establishment of your new seeding before cold weather moves in for the winter,” Hentschel said. “In northern Illinois, for example, fall seeding is best done mid-August through mid-September. Any later than that and you gamble that the new seedlings will be hardened off in time before cold weather arrives.

“For central Illinois, you can go a little farther into September and in southern Illinois usually to the end of September.”

Fall is also a great time to put down fertilizer, as most of our grasses are still putting food into reserves and expanding root systems before cold weather. If you only fertilize once a year, fall is the best time—just stay away from high nitrogen fertilizers in the fall.

“Another cultural management practice that is beneficial to the lawn in the fall is core aeration,” he said. “This opens up compacted soil from traffic patterns made by kids, pets, or—next to the driveway—by car tires hitting the lawn.  Knotweed is a good indicator plant for compaction.

“Core aeration is also great for managing the thatch layer that develops in your lawn. Thatch will catch the water and prevent it from getting down into the soil. As a result, grass roots tend to stay near the surface rather than growing deeper into the soil. Leave the cores on the surface and let them dry out. The next time you mow, they will break up and disappear. You can rent these machines and split the cost with a neighbor.”

A fall broadleaf weed control will eliminate the need for a spring treatment to get rid of dandelions. Because lawn weeds are also putting food reserves into their root systems, fall treatments often give better and more consistent results than a spring application.

“Continue to mow the lawn as long as the grass grows,” he said. “This might mean wearing your coat and gloves for that final mowing in late October or even into November.

“One of the easiest ways to make sure your lawn looks good is to have a sharp mower blade. This is very important if you are using a mulching-style mower. A dull blade will not cut cleanly, leaving a ragged, uneven cut.”