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What is the origin of thatch problems in lawns?

The first seven years with a new home lawn has been called the "Honeymoon" period.  Most of the reason is the absence of a harmful thatch layer over 1/2-inch thick. Up to 1/2-inch of thatch is considered alright, with minimal thatch even being considered beneficial. However, when thatch exceeds 1/2-inch in depth, serious problems begin to occur.

One of the main contributors to thatch development is heavy nitrogen fertilization. Some varieties of grass, such as Kentucky bluegrass, tend to produce thatch due to the growth habit of their roots (rhizomes). Heavy clay soil can also contribute to rooting close to the lawn surface instead of into the soil beneath. Aerating a lawn annually helps to combat this poor rooting situation as well as preventing thatch build-up.

Thick thatch layer
A thick thatch layer on this home lawn
created an ideal home for
destructive grubs

Mulching clippings will not contribute to thatch in normal situations, where there isn't already a thatch problem already. In heavily thatched lawns it will be beneficial to bag clippings, since they are less likely to reach the soil surface where they can breakdown naturally.


To prevent future problems with thatch, there are several measures which can be practiced annually, preferably in the early fall (September):

  • Core aeration done once or twice annually, involves "plugging" the lawn with a "hollow-spoon" aerator

  • Dethatching once every year or two, involves mechanically removing some of the dead debris from the lawn surface

  • Proper soil pH, usually maintained by liming every 3 to 5 years, will encourage the natural breakdown of thatch

In cases where thatch build-up has exceeded 1-inch, we recommend stripping the lawn with a sod-cutter and starting a new lawn.  At this level of thatch, it will take several years to reduce the thatch to an acceptable level, and the cost in the long run will be close to the same. Seeding a new lawn also allows for the introduction of improved turfgrass varieties which weren't available 50 years ago.


sod cutter
Sod-cutter set for 18-inch widths

lawn thatch
Thatched lawn (top)
Soil level (bottom)

cut sod
Sod stripping in progress


Spot-seeding lawns

Growing Lawns in Shade

Grow lawns using low maintenance


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