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Do Dethatching Lawn Mower Blades Work?

Sometimes automation is not all it’s cracked up to be, and that’s certainly the case with dethatching lawnmowers – which according to experts do not seem to work.

Dethatching lawn mower blades are meant for smaller gardens, but are ineffective. So if you have under 1/2 inch of thatch it’s best to get a rake and do it by hand. For larger gardens with over half an inch of thatch, you can use a power rake, which is a more robust machine.

Let’s consider what dethatching is, when and why you need to do it, and look at alternatives to dethatching lawnmowers.

What is Dethatching & Do I Need To Do It?

Thatch is the layer of plant stems, both dead and alive, and organic debris that forms below the green grass tips and above the soil. Over time, too much thatch will kill grass shoots, resulting in a lawn with patchy, brown spots.

To determine your amount of thatch, use a sharpshooter shovel and dig into your lawn, down to the soil, then look at the cross section. Experts say that over 1/2 inch of thatch can be unhealthy for your lawn. If you have one inch or more of thatch, then you need to act. 

Dethatching can help your lawn stay healthy. When thatch is too thick, your watering becomes ineffective – water can’t reach the roots. Pest insects and pathogens can set up a home in thatch. Excessive thatch weakens the lawn’s natural tolerance to disease and dry spells.

Lawns with heavy thatch are brown. Dethatching allows new grass shoots to grow into the dethatched gaps, giving you a lusher, greener lawn.

For southern lawns, experts recommend dethatching your lawn in the spring, every 1 or 2 years. Plan to dethatch your lawn just when the grass starts to green up. If you can’t dethatch in the spring, fall is the second-best time. 

For northern lawns, dethatch in late summer or early fall. For expert advice on dethatching timing, call the Agricultural Extension office in your area.

For dethatching lawns, you can use a normal rake, a hand-held dethatcher rake, get a dethatching blade that fits on your lawn mower, use a dethatcher machine (or scarifier, vertical lawn mower or verticutter) or use a power rake.

Do Thatching Mower Blades Work? (What Are they?)

Exerts and homeowners alike say no, dethatching mower blades are not the best way to dethatch your lawn.

Dethatching mower blades are quite different from regular mowing blades. Regular mowing blades are mostly flat and slice through grass.

Dethatching mower blades, like the one in this video, have tines or spikes that stick out perpendicular to the blade and cut down into the thatch like a knife, slicing it up. 

Some dethatching mower blades have two tines, one on each end of the blade. Some blades have more. Tines are often metal, but some are a tough plastic.

The problem is – thatch is tough stuff. Really tough. 

Most complaints about using dethatching mower blades stem from the mechanical process itself. The mower blade has long metal spikes that spin around in circles, digging through dense stuff – at top speed. That’s hard work.

Spinning long spikes around in a circle through thick thatch needs some serious horsepower. If you have thick thatch, or the grass is a little wet, or you hit a high spot, the blade will have a hard time and your mower engine may burn out. That’s big bucks.

Another common complaint is that the circular motion of the tines can rip out the grass by the roots. Some folks complained that lawns that originally just had thatch problems ended up “scalped”.

Another common complaint is that, if you walk too slowly, you tend to cut large circles in your lawn. Yup – crop circles – in your lawn. 

So – as dethatching blades are meant for smaller gardens, if you have under 1/2 inch of thatch it’s best to get a rake and do it by hand. For larger gardens with over half an inch of thatch you can use a power rake (more on this below).

Lawn dethatching

How To Dethatch a Lawn With a Mower Attachment

If you do still want to give it a go with a dethatcher despite the experts advice – then proceed with caution. Here are some steps to follow:

Firstly – stop watering your lawn. Wait until the lawn has dried completely and then mow your lawn to a low level. If your grass is long, use a grass catcher. Then, detach the grass cutting blade.

Read and follow the instructions carefully for the dethatch blade. Some instructions recommend that you take out the spark plug for safety.

Set the mower on a hard surface, like cement, and take a look at the tine clearance. Cell phone cameras are good for this or raise the grass catcher door. Raise or lower the mower wheels until the tine clearance is 1/4 to 1/2 inch. The height of the tine is key. Too low, and you will dig into dirt. Too high and the mowing will be ineffective.

Empty the grass catcher and put it back on. Pick a test brown patch. Mow over the test patch and see whether the tine is thinning the thatch. Check inside the catcher, if you have one. Do you have cut up thatch inside? Dirt? 

If the tine is cutting down into the soil, then it needs to be raised a little. Make height adjustments using small test patches until the tine is thinning the thatch but not digging into the dirt.

Then, get your earbuds and eye protection on, and do the entire lawn. Cut thatch (and there will be lots of it) makes great compost. Be sure to water it a little more than normal grass clippings, as thatch is drier.

Should I Use a Power Rake Instead?

If you have thatch over 1/2 inch thick and a large lawn, use a power rake.

Power rakes are different from dethatchers, although there is some confusion about the definitions. Most experts agree that dethatchers are smaller machines, appropriate for small lawns. Dethatchers will work well if you have a small amount of thatch – up to 1/2 inch. Dethatchers may look like small lawn mowers, but the blade system is different. 

Dethatcher tines don’t spin around a central point like dethatcher mower blades. On a dethatcher, rows of tines or blades rotate around a long cylinder, like a tiller. The dethatcher blades cut parallel to the direction the machine is going – no crop circles.

Power rakes are larger, and heavier, machines. They can remove much more thatch than dethatchers. Their blades can be flail types or solid knife types. Generally, power rakes are for thick thatch problems and large lawns.

Power rakes can be aggressive. Be sure to rake at times when your lawn can recover before stressful times of the year, like hot summers or freezing cold winters. 

How To Dethatch a Lawn With a Power Rake

First, test a small area with the highest rake setting. Check the results – did it remove all the thatch? If not, lower the rake by one setting and test again.

When you are satisfied that the rake is on the best setting, run the rake in one direction over the entire lawn. Collect all the thatch and debris by hand with a rake or with a lawn mower with a bag attachment. If the thatch debris is dry, you can try to blow it into a pile or onto the street where you can sweep it up.

Once the debris is clear, run the rake in the opposite direction across the lawn. Then, clear the debris. Here’s a great video.

Thatch debris is great for your compost bin and there will be giant piles of it. 

Final Thoughts

You asked a very clear question to find this article: ‘Do Dethatching Lawn Mower Blades Work?’ – and the answer according to most experts in a resounding ‘no’.

There are better ways to thin the thatch on your lawn, especially if you have a smaller garden with under half an inch of lawn thatch. In this instance, using a rake and some good old fashioned elbow grease is the best option.

And if your lawn is bigger – and has a deeper layer of thatch over half an inch think – then choosing a power rake is the more effective way of getting the optimum results.

Mark H.

Homeowner and property investor Mark H. aspires to bring you the very best outdoor living content, based on his years of experience managing outside spaces. Read more >