Why Worry About Thatch? 

 The average lawn contains over 8,000,000 individual grass plants. These plants are always  forming new parts and losing old ones. Thatch is the matted layer of dead and living stems, roots,  and organic matter that forms in most lawns above the soil. Thatch is a natural part of growing turf, and a small amount is actually healthy. It conserves moisture and provides a source of new  humus as it decomposes. 

So Why Do We Hear So Much About The Dangers Of A Thatchy Lawn? 

When the soil in your lawn can't break down thatch as fast as its building up, a lot of problems can result. Thatch over 1/2" thick becomes a breeding place for both insects and diseases. Heavy thatch also encourages turf roots to stay in the thatch layer instead of pushing into the soil.  Another big problem with matted thatch is how it sheds water. The principle is the same as the  thatched roofs used on old-style cottages. By being thick and heavily matted, the surface keeps water out. Thats fine on a house, but not on a lawn. For all these reasons, its important to manage thatch levels as part of a good turf maintenance program. 

Soil And Grass Type Affect Thatch Levels 

Some soils are able to break down thatch very quickly. Soils that are high in microbial activity can  keep up with thatch naturally, eliminating the need for other management practices. Loam soils tend  to handle thatch much better than either clay or sand. 

The variety of grass being grown makes a big difference too. Some turfs are prone to rapid thatch accumulation (kentucky bluegrass and fine fescue for example), while others develop little or no thatch (like tall and improved tall fescues). Conditioning the soil before seeding and then choosing a thatch resistant  variety are two of the best thatch preventive measures. 

Once You Have It, How To Fix It? 

In severe cases (3/4"-1" or more of thatch), stripping or complete tilling and reseeding or sod may be the only solution. Dethatching removes a lot of thatch but also disrupts the good turf, or slice (slit) seeding can be considered. 

Of all the choices for thatch control, core cultivation (or aeration) is the best way to reduce and control thatch. Aeration is simple, economical, and doesn't tear up the entire lawn. Regular core cultivation benefits the entire lawn while solving moderate thatch problems. Aeration also keeps thatch from becoming a serious problem by speeding up the decomposition process and punching through the thatched roof over your soil. 

  Sidebar Points: 

       A little thatch is good, a lot of thatch isn't. 
       Good management keeps thatch under 1/2". 
       Reseed with thatch resistant turf types. 
       Aerate regularly to avoid more costly and severe solutions.