Dethatching, Or Scarifying

Thatch is dead grass and plant material that nature has not been able to break down. Instead, it has formed an impenetrable layer below the grass. 

When the thatch layer exceeds .2 inches, the water permeability of the soil decreases, the grass roots grow closer to the surface and the root mass and the oxygen exchange decreases.

As a result, the grass becomes less durable and can no longer withstand the foot traffic it once could. In addition, the risk of disease increases dramatically and some grass varieties cannot survive.

Thatch forms for a number of reasons, for example:

  • The use of modern, lab-created grass varieties
  • The use of fertilizer with high acidity
  • Over-fertilization

When Should You Dethatch Your Lawn?

It is a good idea to dethatch when the grass is growing well, preferably in late spring or early autumn. Avoid dethatching in early spring or during dry periods, as you may stress your lawn.

Ways Of Decreasing The Thatch Layer

To remove the thatch layer you can use a variety of tools. Dethatching machines with flail blades are a good tool. For more sensitive grasses, a dethatching machine with spring tines is recommended.

You can borrow, rent or purchase a scarifying machine, or you can scarify your lawn by hand using a spring-tined rake. Draw the rake over the lawn in short sweeps, digging the tines into the top level of the soil. Work in one direction across the lawn and then again at right angles to your initial sweep.

Scarifying machines are essential for larger lawns (unless you feel you need the work-out!) and they will usually pick up the thatch for you. Once you have completed the scarifying process, mow the lawn, collecting the clippings, to remove the thatch and even up its appearance.

If you have a great deal of moss in the lawn, you may wish to consider applying a moss killer. If you garden organically and have a problem with moss, it's usually because of inadequate sun or poor drainage. Consider the viability of lawns in shaded or damp ground.

Other Benefits Of Dethatching

A dethatching machine can also be used to cut the lateral roots of the grass and to fight broadleaf weeds. This is most effectively done with a delta blade.