Over the winter, a layer of dead material builds up in a lawn called thatch. This includes dead blades of grass and leaves that can accumulate. It can be more problematic if you mow your lawn and leave too many clippings rather than bagging or raking after mowing. While they do contain organic material, too many clippings can actually become a barrier for moisture and applied fertilizers or organic soil additives. It can prevent them from reaching the soil and, ultimately, the roots of the grass. Some mulched clippings are ok to leave on your lawn. Heavy thatch in the lawn also increases the risk of fungal problems because it provides a moist, organically rich layer for fungus growth.
Dethatching is recommended in the spring to lift up the dead and overgrowing layer on the surface of the grass. It can be done using a specialized dethatching rake, which has thick, curved tines, or it can be done by a specialized piece of equipment that looks like a combination of a tiller, lawnmower, and snow blower. It is important to complete dethatching when the soil is moist and when the lawn is growing, not before it turns green. Depending on your typical spring conditions, some areas of the country may find that dethatching, as well as aerating the lawn, are better done in the autumn.
Aerating is the process of pulling out small plugs of soil to allow better absorption of water and nutrients into the root structure. It is particularly important in areas with clay soils or soils that compact. When the soil is compacted, it is very difficult for the roots of the grass to grow down into the soil, so they tend to stay in a shallow layer. Shallow root structures in lawns result in more damage with hot, dry, conditions, greater risk of root damage with excessive moisture, and less durability for grass when heavy traffic or pets are an issue to consider.
Aeration of a lawn is done with a machine to provide the necessary coring or pulling out of the plugs of earth. Generally, if aeration is done in the spring with an established lawn, it is essential to also use a pre-emergent herbicide to prevent weed growth. If the aeration is done in the autumn, the use of a spring pre-emergent herbicide is not necessary for most areas unless there is year-round growth. Another benefit of autumn aeration of the lawn in more northern areas is that the snow and melt cycle helps to breakdown the plugs of soil left on the surface, leaving your lawn free from the small clumps.It is the best lawn care practice for spring in Chicago
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