Fall aeration leads to a healthier lawn
Q. Sept. 15 is National Aerate your lawn day. I thought you were only supposed to aerate your lawn in the spring. Can you explain?
A. Fall has arrived, so yes, it is time to aerate, top dress and overseed your lawn to improve soil conditions. In the spring, you can look forward to a healthy, thicker lawn.
Spring aerification can allow for a weed invasion and is usually followed with a pre-emergent herbicide application. Spring aeration needs to be done before spring weeds start to germinate and that happens when the soil temperatures reach 55 degrees Fahrenheit. In our area this occurs in April or early May. Spring aerating during this time frame will minimize weed seeds.
Fall is the best time to aerate your lawn though. Core aerating on a regular basis loosens up compact soil and helps break down thatch. Core cultivating can be done yearly; for sod on clay, twice yearly aerification may be necessary. Contrary to popular opinion, fall is the best time for lawn care. Fertilization, weed and thatch control and renovation of poor quality lawns should be done over the next few weeks.
Thatch in turf is a layer of living and dead organic matter between the soil and green vegetation. The amount of thatch in the lawn can be checked by cutting three to four inches down into the grass with a shovel and lifting up a piece of sod. Thatch looks like a thick tangle of dark brown roots above the soil level. If the thatch is greater than one-half inch, the lawn should be core aerated or dethatched in fall. In lawns with a thatch layer over three-quarters of an inch thick, you should aerate then top dress with a thin layer, one-eigth to one-quarter inch, of soil or compost. Top dressing adds microorganisms that help breakdown thatch.
When thatch exceeds one-half inch in thickness, a number of turf problems can develop. Excessive thatch creates a favorable environment for many turf grass insects and diseases. It also creates an unfavorable growth environment by decreasing turf grass cold, heat and drought tolerance.
Two of the biggest contributors to thatch buildup are heavy nitrogen fertilization and irrigation because they cause turf to grow faster and as a result produce more organic matter. Small grass clippings contribute little to thatch buildup. Grass clippings usually are more than 75 to 85 percent water, and as they dry their weight and size are greatly reduced.
Fall is a great time to aerate your lawn. Aerating loosens up compact soil and helps break down thatch. Aeration is best done with mechanical devices that remove plugs of turf and soil from the lawn and deposit them on the surface. The actual removal of a plug is crucial to the breakdown of thatch. Bringing some of the soil to the surface through aeration exposes the thatch to microbes in the soil that will break down the thatch more quickly. There is no need to rake away the plugs, wait one day after aerifying, and mow your lawn, the plugs breakdown in the mowing process.
- Terri Passolt
• Provided by Master Gardeners through the Master Gardener Answer Desk, Friendship Park Conservatory, Des Plaines, and University of Illinois Extension, North Cook Branch Office, Arlington Heights. Call (847) 298-3502 on Wednesdays or email northcookmg@gmail.com. Visit web.extension.illinois.edu/mg.