WHAT CAUSES LAWN THATCH ACCUMULATION?

What is Thatch?

Lawn thatch is composed of a tightly intermingled layer of stems, leaves and grass roots, which accumulates between the vegetation and the soil. Too much thatch increases the turf's susceptibility to lawn diseases, reduces its tolerance to drought, cold, and heat stress; and hinders the movement of air, water, fertilizers, and nutrients into the soil. In severe cases roots of the grass will not grow into the soil but only take root in the thatch layer making the turf susceptible to drought and heat stress.


What Causes Thatch to Buildup?

Thatch will accumulate in a lawn if the production of dead material exceeds the ability of the microorganisms in the soil to break down the organic matter. Thatch build-up occurs in lawns that have "dead soils" and is caused by an absence of beneficial microbial activity. Thatch buildup happens if there is poor soil aeration and drainage, improper lawn watering practices (usually too much water or too frequent water), cold temperatures, the use of chemical pesticides, and the use of synthetic fertilizers.. When a lawn's thatch layer is greater than 3/4 of an inch thick it may need to be mechanically removed.

Note: 99%+ of lawns DO NOT need to have the thatch removed via power raking or vertical raking. Please contact your local lawn care expert before scheduling a power rake.

If a lawn is building thatch faster than the microbes can break it down, this indicates that the lawn is lacking beneficial microbes. The cure to a thatch problem is not physical removal of the thatch, but by managing thatch in a lawn by stopping the improper cultural practice that is killing microbes in the soil.

Managing Thatch in a Lawn

More than 1/2 inch of thatch can be a
problem for the lawn.


Improper Lawn Care Cultural Practices That Kill Microbes

Managing thatch in a lawn is easy. Start by stimulating beneficial microbial activity by using proper watering practices, mowing practices, aeration and fertilization.

Power raking is a tool that can be used as a last resort to manage a major thatch problem, but power raking is not the cure of the thatch problem.


Steps to Repair a Thatch Problem in a Lawn:

Managing Thatch in a Lawn - Boulder


Thatch Explained Quickly:
  • Some lawn thatch is good! ½ of an inch or less is a normal amount of thatch.
  • Thatch buildup occurs when the microbes in the soil cannot break down the organic matter as fast as it accumulates. This typically only occurs when there is a lack of microbial activity in the soil.
  • Excessive thatch is caused by the absence of beneficial microbial activity.
  • Excessive thatch is often caused by improper watering practices; usually too much or too frequent of watering.
  • If the thatch layer is greater than ¾ of an inch then power raking is a tool to use to help manage the thatch.
  • Power raking should not be performed after the lawn greens up. Typically power raking is performed in early March.
  • Fast release nitrogen sources (non-organic fertilizers) can stimulate thatch buildup.
  • Aeration or double aeration is a good way to help prevent thatch buildup.

THATCH PREVENTATIVE PRACTICES
  • Lawn Mowing - Never cut more than 1/3 of the blade of grass at one time. Mulching the grass clippings does not increase the tendency to build thatch. Change the mowing height to 2.5 inches in the spring and fall and increase the height to 3 inches or taller in the summer.
  • Lawn Fertilizing - Fast release nitrogen lawn care applications will result in a decrease in thatch decomposition and an increase in thatch production rates. Always avoid high dosages of synthetic nitrogen sources like ammonium nitrate because they are salt based and kill beneficial microbes. Organic fertilizers stimulate beneficial microbial activity in the soil.
  • Lawn Irrigation - Avoid light and frequent watering. Always irrigate the turf deeply and infrequently. This entices the roots of the grass to grow deep into the soil instead of the thatch layer. The lawn may look worse for a few weeks, but deep and infrequent watering will stimulate the roots to establish into the soil instead of the thatch.
  • Lawn Pesticide - Pesticides negatively affect desirable microorganism and earthworm populations. Lawn care pesticides should be avoided unless absolutely necessary.

Managing Thatch in a Lawn - Fort Collins


FAQ - Thatch Buildup

How do I get rid of thatch on my lawn?

  • Thatch only accumulates in a lawn when there is an absence of beneficial microbial activity. Thatch buildup is caused by improper lawn watering, improper lawn mowing, and or the use of chemical fertilizers. The best way for managing thatch in a lawn is to create an environment that stimulates beneficial microbial activity, which is called building a living soil. The microbes in the soil will be able to break down the material and keep the thatch layer to healthy thickness - about ½ inch or less.

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