When to Dethatch Lawn – 7 Vital Tips to Dethatching!

Think your lawn is spongy and needs to be dethatched? 

Let’s look at when to dethatch lawns, why it’s important, and how you can dethatch a lawn in 7 simple steps!

When is the best time to dethatch lawn? The best time to dethatch your grass is at your grass’ optimal growth period. For cool-season grasses, that is early spring or early fall. For warm-season grass, it is late spring or early summer. 

Still, struggling? Take a look at our guide to find out what type of grass you have!

Once you know when to dethatch, the next question is how often should I dethatch my lawn? 

The general rule is that you should try to dethatch your lawn at least once a year for cool-season grasses and a maximum of once a year for warm-season grasses.

Below, we’ll take you through the following:

  1. What is Thatch and Why is Dethatching Important?
  2. How to Dethatch a Lawn
  3. When to dethatch lawn

What Is Dethatching and Why Is It Important?

Dethatching lawn

In general, the grass is one of the easier organisms in your garden to maintain. But the world is a dangerous place, even for its most prosperous plant.

Bugs, disease, drought, floods, and frost can all impair a grass’s ability to take on air, water, and nutrients. Luckily, we can help our grass overcome the elements by providing better avenues for absorption through dethatching and or aerating our lawns. 

Thatch is the name we give a layer of dead grass that sits just above the soil line. It serves the valuable purpose of protecting the grass from the elements and dangerous diseases. Think of it as the blood-brain barrier, but for your green grass instead of your brain!

It should be between ¼ inch – ½ inch in thickness. If your thatch is any thicker than this, it risks stopping vital water and air from reaching the roots of the living grass. 

It’s time to dethatch lawns as soon as you feel them becoming too spongy underfoot. If you’re still not sure, try inserting a standard screwdriver into the lawn. If it requires a lot of force, your grass is either compacted or full of thatch. 

For compacted grass with a healthy amount of thatch, you will want to aerate your lawn. Lawn with thatch above ½ inch thick will want to be dethatched. 

To find out how much thatch you have, dig out a sample of turf and measure the amount of dead grass. 

To dethatch your lawn, you will need to follow the following 7 instructions. Below, we’ll take you through each one step-by-step.

  1. Mow Your Lawn
  2. Scout Area for Debris, Irrigation lines or Automatic Mower Lines. 
  3. Set Height of Dethatcher
  4. Clear Up
  5. Re-seed any Bare Spots
  6. Spread fertilizer
  7. Apply Water

How To Dethatch a Lawn

Step 1: Mow Your Lawn

Lawn mower

The first step in dethatching your lawn is to mow the grass so it sits at a height slightly lower than its usual length. 

Remember that thatch sits below the green, healthy grass and sits just on top of the soil line. Try to mow your grass to around 1.5 inches for cool-season grass and as low as ¾ inch for warm-season grass. 

Any grass that sits at 2 inches and above will likely make it difficult to dethatch as the blades on your dethatcher might not penetrate deep enough. 

Remember the one-third rule! Never take off more than one-third of the grass leaves in one mow. 

When you mow, you weaken your lawn slightly. If you mow too much of your lawn in one sitting, you damage your lawn more significantly and make it harder for the grass to maintain healthy color.

Prep your lawn for dethatching by cutting it to 1.5 inches or ¾ inch for warm-season grass in multiple mowing sessions. 

If you normally have your grass at 3 inches, it may take you two mowing sessions to get down to the ideal 1 – 1.5 inches. Mow once, give your lawn time to settle and recover slightly and then mow again in 4-5 days’ time. 

If measuring your lawn height seems a little too technical for your liking, mow your lawn to half the height you would normally have it.

Step 2: Scout the Area

Small water sprinkler

Another crucial step before dethatching your lawn is to scout the area for anything that could snag or break the dethatcher.

Renting dethatchers is a great way to save on costs but they can often be quite old machines. They’ve been passed around from home to home and not everyone will have taken care of it. You don’t want to be the one covering the bill if you run over your dog’s chew toy. 

Another thing to look out for is any shallow wiring for irrigation or worse, your brand-new automated mower! 

If you have irrigation or an automated mower installed, mark out the outline of the wiring so you know not to go over it with the dethatcher.

Step 3: Set the Height of the Dethatcher

Setting height on dethatcher

Remember a healthy layer of thatch is around 1/2 – ¾ inch. You’ll want to take out enough thatch so it sits around this thickness. 

One way to determine this is to take a small sample out of your lawn using a spade or trowel and measure the thatch layer. 

Most dethatchers will give you a setting based on how thick your thatch is and normally have three simple settings, low, middle, and high. 

The high setting puts the dethatcher at a level higher above the ground and as a result, won’t take as much of the dead grass out. 

The lower you go, the more dead grass you will remove and the more you will ‘damage’ your grass. 

If you have a 2-inch thick thatch layer, feel free to set your machine at the lowest setting as you will want to remove a lot of dead grass. However, if you find a 1-inch thick layer, perhaps try the medium setting. 

If you regularly treat your lawn and find you have a thatch layer of below 1 inch and are simply looking to provide good maintenance, definitely set your machine to the highest level.

Don’t worry too much about damaging your lawn as you will overseed any bare patches and provide feed to the grass in order to help it bounce back. 

You are now ready to dethatch your lawn! Turn on the machine and follow a similar pattern to how you would mow in a simple horizontal mowing session.

Step 4: Clear Up

Clearing lawn with a rake

Much like when we aerate a lawn, we are dramatically changing the ecosystem of the lawn. You will awaken dormant weed seeds and ultimately throw a lot of dead organic material on top of the healthy, living grass. 

This material will need to be cleared up as it is the perfect breeding ground for moss and disease. It will also make it even harder for the healthy grass to receive vital sunlight, air, and water if left on top. 

The best way to clear up thatch is by using a rake, leaf blower, or lawn sweeper. Bare in mind that the leaf blower will need to be quite powerful as thatch tends to be quite thick. 

We normally put a bag on our mower and collect it all in the mower before throwing it on the compost heap. 

If you’re a keen composter as well, make sure you haven’t applied any pesticides or herbicides for at least 6 months prior to dethatching!

Step 5: Overseed Any Bare Spots

Overseeding bare spots in lawn

As you’ve probably realized by now, dethatching puts your grass through quite a bit of trauma. We are essentially cutting the grass by ripping it up from the inside out. Knowing when to dethatch lawn won’t always save you from bare sports so don’t be afraid if some show up. 

The healthy grass underneath the thatch will bounce back quickly if you water it and feed it. 

To make sure you’re not left with any patches of dirt in the middle of your lawn, make sure you have a bag of seed at the ready to spread some seed onto the bare patch. 

You will want to make sure this seed is the same type as the rest of your lawn. With a sprinkle of seed, and some care and attention, the patch will become invisible within a couple of weeks. 

Bare spots are another reason why we want to dethatch at the peak of the grass’s growing ability and why the timing of your dethatching is so important. 

Dethatch too early in the season when your grass is emerging out of dormancy and your grass will take a long time to grow back. You might even find bare patches do not recover until late summer. 

So, take care to find out when the best time to dethatch your lawn is and make sure you overseed any struggling areas of grass.

Step 6: Apply Fertilizer to Your Dethatched Lawn

Applying fertilizer in lawn

Experts disagree slightly over the timing of when you fertilize your dethatched lawn with some advocating immediately afterward and some suggestions to wait two weeks after dethatching. 

The reason some enthusiasts choose to wait is to give the grass an opportunity to recover from the thrashing of the tines on the dethatcher. 

We recommend applying a gentle starter fertilizer in the afternoon in between a sprinkle of water. 

In an ideal world, the heavens would open the night before you dethatch to loosen up the dead grass. It would then be a dry day with dethatching in the morning, a quick shower before blue skies and sunshine while you fertilize your lawn. That night it would then rain heavily to drench the roots for ultimate growth. 

Whatever the weather and whichever order you decide to do things, you will want to apply your fertilizer with a worthy spreader. 

At this point, you’ve put a lot of hard work into your lawn and it would be a shame to use a standard spreader to unevenly distribute fertilizer across your lawn. 

Fertilizer is the food that helps grow your lawn and in many cases, gives it the deep, healthy green color you’re looking for. 

Manufacturers spend huge amounts in the development of their products to provide the optimum combination of elements for premium growth and color. 

Homeowners and professionals alike spend vast quantities on fertilizer but distribute it with a product that spreads 80% to the right side and 20% to the left side. 

How do we know this? Because we test hundreds of spreaders each year to find out about our competitors. 

No matter what brand of spreader purchase, make sure you have the ability to change the spread pattern by opening or closing the left and right holes on the application. 

Before you apply your fertilizer, make sure you calibrate your fertilizer to your spreader. If you’re confused as to which spreader to choose, take a look at our handy article, how to calibrate a spreader.

Step 7: Water Your Lawn

Water sprinkler

Your lawn has been through a lot and so have you! But before you pack up your tools in the shack, make sure you water your lawn. 

If you have an irrigation unit installed, then that’s great but if not, 20 minutes of watering your yard will make the entire day worth it. 

Your lawn will soak in the water overnight which will nourish the deep roots of the grass creating a stronger plant and a better-looking lawn!

When Is the Best Time To Dethatch the Lawn

You now know that dethatching your lawn is important to provide the grass with ample amounts of light, water, air, and nutrients. 

We also know how to dethatch lawn and when to dethatch lawn based on what type of grass you have. 

Remember that you should only dethatch your lawn a maximum of once per year for warm-season grass and between once and twice a year in early spring and autumn for cool-season grass. 

Warm-season grass should be dethatched in late spring or early summer. 

We haven’t covered the best tools to dethatch your lawn in this article, but I can give you a quick clue – rent a dethatcher! It’s a terribly long job if you plan to manually dethatch your lawn by using a rake. Save yourself the hassle and rent a dethatcher.

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