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. This is a good time to
consider what we are trying to accomplish with these practices.
Power raking is primarily a thatch control operation. It can be excessively
damaging to the turf if not done carefully. For lawns with one-half inch of
thatch or less, I don’t recommend power raking but rather core aeration. For
those who are unsure what thatch is, it is a springy layer of light-brown
organic matter that resembles peat moss and is located above the soil but
below the grass foliage. Power raking pulls up an incredible amount of
material that then must be dealt with by composting or discarding.
Core-aeration is a much better practice 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 should be
made so that the holes are spaced about2 to 3 inches apart.Ideally, the holes
should penetrate 2.5 to 3 inchesdeep. The cores can be left on the lawn to decompose
naturally (a processthat 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 doormat. The
intermingling of soil and thatch is beneficial to the lawn.
By: Ward Upham
