E. Dethatching Lawn

Dethatching lawn has become a regular part of preventative maintenance. Most landscaping companies now offer this service, because they know the benefits of removing thatch.

Dethatching, or power raking, pulls up the unwanted organic matter on the surface of the soil called "Thatch". This short how-to module is to help do-it-yourselfers understand if, why, and when they should dethatch.

After dethatching lawn, the organic matter is raked up and disposed of, or composted. This will actually leave you a pretty ragged looking lawn. Although the lawn may not look healthy and attractive, it will be better off for it in the long run.

Dethatching lawn or Power rake? What is the difference?

I have heard people separate the two, and others call it the same thing. There is a difference, and we are going to look at them both. As a homeowner, understanding the effects of each method will help you decide which is best for you.

"Power rake" is a method of dethatching lawn, using a vertical mower with knife-like blades that slice through the thatch. It is also used to thicken up lawns that grow by the spread of stolons. The knives slice through the stolons between the plants (In turn, producing more stems). This will thicken up lawns much faster than if the stolons were not cut.

Dethatching lawn is a method using the same vertical mower with flail type tines that actually tear, instead of slicing. They are the most aggressive way to remove thatch.

The term “dethatch” simply means removing thatch. They both do that, just in different ways. They will be covered further at the bottom of this section in dethatching methods.

What is thatch?

Thatch is a layer of organic matter that accumulates on the surface of the soil. It can be made up of roots, stems, and debris that are deposited faster than they decompose.

Grass clippings also make up thatch, but generally are not the cause of excessive thatch. If proper mowing and lawn care practices are followed, clippings should not be an issue. Please see our mini module on "Mowing" for a better explanation of this.

If you do have a heavy amount of thatch and are planning on dethatching, bag your clippings until you have dethatched.

Thatch can create a haven for pests and diseases in your lawn. It can also create a barrier that will prevent water and other nutrients from reaching the soil.

Preventing Thatch

Some people will dethatch every one to two years, while others think dethatching lawn is very stressful, and should only be done as a last resort. Rather than dealing with the controversy, make preventing thatch a priority in maintaining a healthy lawn.

There are different ways to prevent and control thatch buildup in your lawn, and combining them all will give you the most success.

Core aerating your lawn is an excellent way to control thatch, as it removes plugs that also contain thatch. Plugs from a healthy soil contain microbes that breakdown thatch and turn it into nutrients for the soil. It's like a mini composting system for you lawn.

Watering your lawn deeply but infrequently. (Let it dry between watering.) This will encourage deep root growth and will also help cut down on thatch. Shallow watering can create shallow rooting. Basically, the roots will grow closer to the source of water.(Which is now at the surface.) Over watering or fertilizing can also lead to thatch build up, so give it only what it requires.

Another way to help control thatch is by applying a thin layer (¼ to ½ inch) of compost or topdressing to your soil each year. The compost will feed the soil with nutrients while breaking down the thatch.

Power raking is not quite as aggressive as dethatching lawn. This makes it less stressful and damaging to your lawn. If it is done properly, you can do this yearly. Some people think it is a great way to clean up winter debris to give your lawn a boost for the spring growing season.

When to dethatch?

The general rule of when to dethatch, is when the thatch is a ½ inch in thickness or more. Anything more than one inch would be considered excessive. (It is normal and healthy to have up to this amount.)

A normal amount of thatch can help retain moisture, and protect the soil from drying out quickly in the hot sun.

Like aerating, dethatching lawn is better for the overall health of your lawn, but it does have negative short term effects. Some healthy roots are also damaged in the process.

Dethatching lawn should be planned accordingly and done before the most active growing times for your lawn. This means your lawn will recover faster from the stresses you have just put it through.

Warm season grasses should be dethatched in the late spring, or early summer just before their peak growth time. This will give them a full growing season to recover from the process.

Cool season grasses should also be dethatched before peak growth times. This can vary depending on your climate, how early your spring arrives, and how long the hot summer lasts. The preferred time to dethatch is late summer, when the heat and drought give way to favourable growing conditions again. This gives your lawn plenty of time to recover and prepare for winter.

Some people dethatch in the spring before peak growth time. This is acceptable as well, if you give your lawn plenty of time to recover before the summer heat and drought. Spring dethatching is often done with a power rake, because it is not as stressful on the lawn.

Whatever season you dethatch in, you can overseed any thin or bare patches. You will have your best results if you can keep them moist until they have germinated. You want your lawn to be nice and thick preventing weeds from getting a foothold.

When reseeding, make sure you use a fertilizer that will not affect the seeds you have just put down. Don't use pre-emergents when seeding. Pre-emergents prevent germination in grass seeds, as well as weed seeds.

As with anything in your yard that penetrates into the soil (no matter how shallow it does), be careful of cable, phone, or irrigation lines that may be near the surface.

Dethatching Methods

If you have a small area and are full of energy to burn, you can use a manual dethatching rake. They are cheaper, and there when you need them for doing smaller areas of your yard.

If you have a larger lawn, you should rent a dethatcher from an equipment rental store. If you have never run the equipment before, you may find this physically challenging. You might want to call a local lawn care provider to do it for you. They also will know how much thatch to remove for you, making it worth the money in the end.

Mechanical dethatchers are vertical mowers, with flail type tines that cut into the very top of the soil and tear out the thatch. These mechanical dethatchers can be rented at most equipment rental stores.

Power raking also uses a vertical mower, but with knife-like blades that slice instead of tearing through the thatch. They should only penetrate into the very top of the soil. They should be set a little higher than a dethatching machine and will do less damage to the root system.

There are also dethatching attachments available for your lawn mower blade. Be aware that these have been known to be very hard on the mower. They may not be worth the risk of damaging your mower, and are not recommended.

The last type we are going to cover are the vertical mowers with flexible tines. These are better than the mower type attachments, but still not as effective as the steel blade or stiff tine machines.

Power raking over Dethatching?

Dethaching may be harder on your lawn but it will be the most effective method. Remember that the flail type tines tear out the thatch, causing damage to healthy grass.

Power raking slices, and is not as hard on your lawn. The downside to power raking is that it does not remove heavy amounts of thatch as effectively.

Power raking is an excellent method to use for thickening up bentgrass lawns, and for doing spring clean ups.

Homeowners should always know the type of grass they have, and what it's specific maintenance requirements are.

A few more tips before you begin.

Whether you are dethaching lawn, or power raking, you will probably have to make multiple passes. Each one should be at right angle to the previous one.

  • Don't be too aggressive trying to remove all the thatch all at once.
  • Make sure your lawn and soil are not soaked, or you or you will tear and damage more of the root system.
  • Also, dethatching lawn is something you plan in advance. Don't compost the thatch if you applied any herbicides in the two months before dethatching.
  • Set the height a little higher on the first pass so you get the hang of what you are doing. It's better to be too high, then too low.

That's it for dethatching. We hope you found this helpful? Best of luck with your yard.

Next, we are going to talk about...Topdressing.


Table of Contents: Lawn Care and Maintenance

Introduction: Lawn Care and Maintenance

A. Watering

B. Mowing

C. Fertilizing

D. Aerating

E. Dethatching

F. Topdressing


The Yard: Landscaping How-to Modules



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