Thatch is a layer of dead, decaying plants tissue, and growing root stems that builds up in between the soil surface and the grass.
Thatch absorbs water and nutrients, and the roots of the grass are drawn up rather than penetrating the soil.
Dethatching, Beneficial or Detrimental?
Dethatching can either be beneficial or detrimental to your lawn, depending on the thickness of the thatch buildup. A thin layer of thatch (less than 1/2 inch thick) can be beneficial to the lawn because it helps to limit weed germination, reduce water evaporation, and protect from frost damage. When it gets thicker than 1/2″, it can prevent water & oxygen from reaching the root, can choke out the grass & it can act as a harbor for pests to thrive. Significant thatch buildup in lawns can cause diseases and can encourage moss to grow in the areas where grass has died.
How Can I Slow Down the Buildup of Thatch?
The overall health of your lawn plays a substantial role in thatch buildup. Over fertilization (specifically Nitrogen) can greatly accelerate the natural buildup of thatch. Avoid frequent & shallow watering on established lawns (causes roots to stay close to the surface). Instead, water deeply & less often, as this encourages healthy root development. Despite the common perception, allowing grass clippings to remain on the lawn doesn’t contribute to thatch. Grass clippings break down quickly and encourage the beneficial earthworms and microorganisms that maintain healthy grass and healthy soil. One of the most common mistakes made is cutting the grass too short. For most lawns in Maryland is best when the lawn is mowed at a height of approx 3.5″ to 4.5". Also, having your lawn Aerated on an annual basis with an aerating machine (which pulls plugs from the lawn) can drastically improve both the quality of your lawn & reduce thatch buildup.