September is the optimum time to power-rake or core-aerate tall fescue and Kentucky bluegrass lawns. These grasses should be coming out of their summer doldrums and beginning to grow more vigorously.
Power-raking is primarily a thatch-control operation. It can be excessively damaging to the turf if not done carefully. Thatch is a springy layer of light-brown organic matter that looks something like peat moss and is located above the soil but below the grass foliage. For lawns with a half-inch of thatch or less, power-raking is not recommended.
Core-aeration is a much better practice than power raking for most lawns. By removing cores of soil, core-aeration relieves compaction, hastens thatch decomposition, and improves water, nutrient and oxygen movement into the soil profile. This operation should be performed when the soil is just moist enough so that it crumbles easily when worked between the fingers.
Enough passes with the core aerator should be made so that the holes are spaced about 2 to 3 inches apart. Ideally, the holes should penetrate 2 1/2 to 3 inches deep. The cores can be left on the lawn to decompose naturally (a process that usually takes two or three weeks, depending on soil type), or they can be broken up with a vertical mower set just low enough to nick the cores, and then dragged with a section of chain-link fence or a steel door mat. The intermingling of soil and thatch that results is beneficial to the lawn.
-- The Garden Calendar is sponsored by K-State Research and Extension-Douglas County office and written this week by Bruce Chladny, horticulture extension agent. For more information call the Master Gardener Hotline, 843-7058, between 1 p.m. and 4 p.m., Monday through Friday.
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