Q: I’ve read that late summer is the time to get my lawn ready for the coming winter and next year. Is this true, and if so, what is needed?
A: In northern Illinois, falling average temperatures and increasing rainfall combine to make late August and early September the best time for several critical lawn-care tasks.
Prepare: Remove weeds by hand-pulling or spot application of a broadleaf herbicide, then mow the entire lawn.
Aerate: Core aerate the lawn to reduce soil compaction and introduce paths for air, water, and nutrients to reach the roots. Most landscape services will perform this task, or hollow tine machines can be rented. Let the soil plugs dry for at least one day before mowing to break them up.
Fertilize: A late-summer application of an organic or synthetic fertilizer will help turf recover from the stresses of summer. It is helpful to have soil tested and select a fertilizer formulation based on test results. Limit nitrogen application to a maximum of 1pound per 1,000 square feet of lawn during one application. If you plan to overseed or renovate areas of the lawn, avoid fertilizers containing herbicides.
Optionally, a winterizing fertilizer can be applied when top vertical growth has stopped, but while the turf is still green and photosynthesizing, which is usually one week after the final mowing of the season.
Topdress and overseed: Apply a grass seed mix suitable for the shade level of your lawn to the entire area at 50 percent of the rate specified for new lawns. Cover with a thin (1/8- to ¼-inch) layer of compost and rake or drag it into the turf. Complete this step no later than the first week of September.
Address problem areas: Large, bare, or thin spots and areas of significant weed infestation require additional effort. Clear large weed infestations by covering the area tightly with black polyethylene sheet for four to eight weeks to block sunlight, or applying a non-selective herbicide. When using garden chemicals, always read and follow the safety and application instructions attached to the product label. Prepare the areas that you wish to reseed by tilling, rough grading, and removing debris. Amend the soil as necessary, mixing the amendments to a depth of at least 6 inches. Fine grade and apply a seed mix suitable for the shade level of the area at the rate recommended by the seed supplier. Mix the seed into the top ¼-inch of the soil with a lawn rake. Cover with a thin layer of straw.
Care: Lightly water the overseeded and reseeded areas immediately after seeding. Continue to water lightly but frequently (typically once or twice a day) until the seed germinates, in 10 to 14 days. After about two weeks, water deeply once per week to encourage strong rooting. Mow carefully once newly geminated grass reaches normal mowing height.
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