Thatch is a problem in many lawns, sometimes without the gardener even knowing it. It invisibly reduces the effects of fertilizer and seeding. In the worst cases it can destroy the appearance of your lawn and impede vigorous growth. Reducing thatch is necessary for the healthiest lawn possible from season to season.
What is Thatch?
Thatch, according to the University of Illinois Extension, is a layer of living or dead plant material that lays between the soil surface and living green material. Thatch exists in most lawns but is exacerbated by dull mower blades and poor cultivation practices.
When is it a Problem?
Thatch is a problem once it reaches a thickness of 1/2 inch or more. Thatch at this thickness reduces the amount of water reaching the soil and fertilizer absorption. It also becomes a small ecosystem for pests and disease. Grass roots have a hard time growing through thick thatch.
Regular, moderate fertilization grows a vigorous, dense turf that reduces thatch development. Cutting grass blades so that only one-third is removed at a time also reduces thatch accumulation. Sharp equipment prevents large chunks of organic material being pulled up from the soil. Regular irrigation and aeration of the lawn to increase air circulation in the soil breaks down developed thatch.
The University of Missouri Extension recommends removing 2- to 3-inch deep plugs from the soil in several locations in the lawn to determine whether the thatch is at a depth that requires removal. Power rakes are available from most garden centers for the removal of thatch. Thatching is best done in mid-June for most turfgrasses, when the lawn is actively growing, to ensure recovery. Cool season grasses are best thatched in the fall.
Core aeration, the removal of 1-inch plugs of dirt throughout the yard is another method of reducing thatch in the lawn. Plugs of dirt have microorganisms in them that break down lawn thatch. Raking the plugs after aeration spreads the dirt over the thatch.