Once this is accomplished, the next two lawn care practices to consider are core aeration or power raking. Both practices can be done from late March through April, or in September. If completed in spring, it’s important to allow soil to dry before doing either practice.
Core aeration removes cores of soil to relieve soil compaction which occurs from irrigation, foot, and mower traffic. Aerate each year on lawns growing on silt loam or clay soils and those which have a lot of foot traffic. Lawns on sandier soils and having little foot traffic can be aerated less often.
By relieving soil compaction, the infiltration of water, fertilizers and soil applied pesticides is improved. Pore spaces in soils are enlarged to improve water drainage and increase oxygen levels. Thatch also builds up more slowly. This promotes deeper, healthier roots which leads to healthier top growth and fewer diseases, insects and weeds.
Power raking is recommended to reduce true thatch once the layer exceeds one-half inch. True thatch cannot be seen from the surface. Some people power rake for cosmetic reasons. Their goal is to remove some of the dead debris they can see on the surface of the lawn. In these cases, the lawn is given a light power raking.
True thatch is a reddish brown mat found between the soil line and turfgrass crowns. It consists mainly of roots, rhizomes and stems. Grass blades contribute little to thatch and so thatch builds up whether grass clippings are caught or left during mowing.
One-half inch layer of thatch is beneficial. It acts as an insulation layer for the growing crowns that extreme heat and cold and foot traffic cause. If a lawn is power raked too often and too deeply, this true thatch layer may not build up to a beneficial point.
Once the layer exceeds one-half inch, thatch becomes detrimental to turfgrass. Roots tend to grow in thatch instead of the soil, water does not infiltrate as readily, and fertilizer and pesticides can become tied up in thatch.
Check your true thatch layer about once a year and check for it in more than one area of the lawn. To measure true thatch, cut a small pie-shaped wedge, or plug and pull it from the lawn. Look for the reddish brown mat between the soil line and the green grass, then measure it. If true thatch is greater than one-half inch thick, it’s time to think about power raking. However, don’t forget to core aerate. Aeration is one of the most beneficial practices you can do for a healthy lawn and it should be done about once a year whether you power rake or not. Core aeration also slows down the build up of thatch. If it’s done often, a deep power raking may rarely be needed.
