Dethatching Lawns: the What, Why, How, and When

Thatch Removal an Essential Part of Keeping Grass Healthy

Don't scalp your lawn if you want to have healthy grass (image).
A beautiful lawn like this one does not happen by accident: you can be sure a lot of care has been put into it. David Beaulieu

"Dethatching" lawns refers to the mechanical removal from a lawn of the layer of dead turfgrass tissue known as "thatch." This residue is bad for your grass, as it keeps water and nutrients from seeping down to grass roots. Preventing thatch buildup is not nearly as big a part of lawn care as is mowing, but you should not overlook its importance to the long-term health of your grass.

Now that you know what dethatching is and why it is important, let's consider how and when to do it.

The How: Dethatching Proper and Core Aeration

While the process of thatch removal is what is technically called "dethatching," there are actually two distinct methods for dealing with the problem of thatch; which one you use will depend on the severity of the situation:

  1. In dethatching proper you use a rake
  2. Core aeration requires a mechanical device

Pushing rake tines deeply down into the grass when you are raking leaves in the fall or raking to clean up the lawn in early spring is an easy method that you can use for dethatching lawns. A convex or "dethatching" rake is better than a regular leaf rake (and a so-called "power rake," which can be rented from a rental center, is the best rake of all), but any rake is better than nothing. Regardless of the rake that you employ, the raking method will be sufficient only when cases of thatch buildup are relatively minor. 

In worse cases, core aeration may be necessary for dethatching lawns properly.

If you have badly compacted soil, that is another reason to aerate your lawn.

You have three options when it comes to core aeration:

  1. Hire a lawn service to do the job
  2. Rent a core aerator
  3. Buy an aerator

My advice to the average homeowner would be either to hire a lawn service or to rent a core aerator. When it comes to buying, not only is cost an issue, but so is storage.

Dethatching a lawn by means of a core aerator is probably not going to be a yearly task. Do you really have enough space in your garage or storage shed to store an extra piece of large equipment that you might not even use some years? An exception might be made if you own a tractor or a riding lawn mower, because you can buy an attachment for these machines that will allow you to aerate your lawn.

And how would you pick between the other two options? Well, if you are not physically up to the job, do not live near a rental center, or just plain do not like gadgets very much, it might make sense for you to choose to hire a lawn service to do this work. Otherwise, renting is a great option.

The When: the Best Time for Dethatching Lawns

When the best time is to dethatch your lawn depends on whether you grow a cool-season grass or a warm-season grass. If the former, dethatch either in early spring or in early fall. This is when the cool-season grasses are coming into their prime time for growth (which will help them recover quickly from the stress of being dethatched). Dethatch lawns composed of warm-season grasses in late spring, which is just when they are "coming into their own."