Thatching in lawns, or lawn thatch, is the grass cuttings or dead grass that manifests itself between the lawn grass surface and the soil line. This is not always bad, as microbes will break down the thatch, and convert it to a nutrient that the plant can use. It becomes a problem when the build up is too excessive. So consider this thatching as, “good”.

Good thatching is a layer of 10 mm or half of an inch thick, which consists of grass clippings, and dust particles that settle from the atmosphere. Within this layer are microbes that decompose the clippings and create nutrients for the plant. This is a natural progression of decomposition, seen in forests and other such areas, where the falling leaves and other dead material converts to plant food. However, it is the control of the thickness of this layer of thatch, that determines the good, the bad and the ugly.

The fact that thatch is present, assists in the saving, of fertilizer costs due to supplemented nutrient supply, irrigation applications due to the reduction in moisture evaporation, and good microbial reproduction promoted.

In parts of the world where the watering of lawns cannot be left to the natural precipitation, and consequential replenishing of ground water tables, excessive thatching is a major problem. Precipitation or irrigation needs to penetrate the top surface soil areas and sink to the lower substrata, for root zone development, if the thatch build up is excessive, this will not occur. Water will run off to an area where it can penetrate the soils. So consider this thatching as, “bad”.

Bad thatching, or an excessive build up, is easily noticed after a heavy rain or irrigation. The excessive thatch will appear as dead grass, not yet decomposing, that will float on the run off water and appear as dead grass ridges where the water has penetrated the soils, depositing the thatch on the surface of the lawn. Excessive thatch becomes breeding grounds for unwanted “bugs” and pests, that will start to manifest themselves and become problematical in the future. Water penetration and fertilizer applications appear not to have an effect on the lawn. Drying out of the soils, and root zones is the consequential result with dying off and fungal diseases being the result.

Where the thatch build up is of such a standard, that there is a reduction in the grass crowns, a thinning of the growth of stolons and rhizomes, with signs of developing anaerobic conditions, this would be the considered the “ugly”.

The ugly thatching, is considered the “almost too late stage of lawn care”. Immediate remedial steps, required when thatching has reached this stage. Remove thatch, with machines designed for this purpose, or undertake heavy raking of the grass surface. Aeration of the soils, should follow with a good fertilizer and even a light topdressing of soil.

On golf greens, Course Superintendents, use the “dusting technique”, this is a fine application of dust, brushed into the surface of the grass, that assists the control of excessive build up. A golf green would never be allowed to have a large build up of thatch, but a small amount is unavoidable, as no mower will completely retrieve all grass clippings.

Maintaining a “good” thatch, do not allow an excessive build up, and undertake light top dressing.

The “bad” thatch, control with periodic raking and then top dressing, and watch for the signs of excessive build up.

The “ugly” thatch, react immediately before it is too late, and avoid the total loss of the lawn.

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