Removing Thatch From Lawns

Thatch… recognizing it, and removing it!

Lawn DethacherThatch is a communion of dead grass, roots and other matter that builds up in grass over time. Its very common and collects on most lawns at some time or another. Thatch collects above the soil at surface level and becomes intertwined in grass stems. When the cycle of decomposition is delayed for any variety of reasons, dead matter will begin to build up. As the build up increases the dead matter becomes stacked and then packs down or matts and causes healthy grass blades to become stressed and weaken.  It thins, and eventually dies.

Thatch can actually choke a lawn to death! As it thickens it robs the soil of air and hinders water absorption and nutrient penetration to the soil and root system. Not only will excessive thatch kill the grass, left undeterred long enough it will damage the soil so that even if removed, new growth in that area will be sparse at best. Thick thatch levels can also become a haven for insects. Moisture rich matted thatch can be an excellent breeding ground for mosquitos and disease.

Thatch creates a water barrier, prevents new grass from growing and harbors insects. It collects quickly and before long the lawn and its entire root system is at risk.

Lawn dethatching (also called power raking), when performed as needed, will go a long way in maintaining a healthy, green lawn! Dethatching allows new grass shoots to grow in thick and lush.

Controlling Nuisance Thatch

A thin layer of thatch, up to a quarter inch, is common and easily controlled with a Dethatcher. Dethatchers are powered rakes. Also commonly known as turf rakes or power rakes, they grapple at the soil surface lifting dead matter to the top of the lawn so it can be removed. Dethatchers, or turf rakes utilize layers of pliable steel combs that lift thatch to the surface. The thatch can be collected and placed in the compost bin, or discarded.

Moderate Thatch

When thatch levels exceed a quarter inch to about a half of an inch, you have a moderate thatch problem. By definition, turf rakes only scratch the surface. By this time the problem may have affected the upper soil level. Dethatching will help control the problem, though odds are, even if dethatched thoroughly at this point there will be bare spots left behind and the remaining grass in the area affected will be sparse and weak. Dethatching followed by seeding and fertilizing may be remedy enough for the soil and help the lawn recover.

Excessive Thatch… and the Need for Aeration

When thatch levels are a half an inch thick or higher and any new growth is weak and sparse, the root system is being compromised. In time, thatch will compact the soil and suffocate the root system. Soil aeration will be needed to loosen the soil to allow air, water, and nutrients to penetrate the root system. An Aerator would offer the starved soil much needed air and nutrients.

You Should Consider Dethatching or Power Raking Your Lawn if:

1. You have a lawn comprised of cool season grass or grasses, the most common of which are perennial ryegrass, Kentucky bluegrass, and fescue. Cool season grasses grow where the winters are colder; they spread by producing underground rhizomes.

2. Your lawn has spots where the grass is very thin where the individual grass blades are weak and far apart from one another.

3. Your lawn has large brown spots where the thatch is so thick that it has temporarily suppressed all or most of the grass plants in that area of the lawn.

4. Water runs off your lawn before it can penetrate the soil. This is especially problematic on sloping areas, where thatch prevents a barrier to water absorption.

5. Your lawn is severely compacted by heavy foot traffic, and you are planning to aerate it, or have it aerated professionally. (Thatch build-up should always be removed before aerating a lawn.)

6. You are planning to over seed your lawn this fall (which is always a good idea).

When to Dethatch Your Lawn

Depending on where you live in the country, and if you have cool-season grass or warm-season grass, you should dethatch in early fall before you fertilize, or in the spring after the grass has begun to green.

Timing is very important; you can actually do more harm than good if you dethatch at the wrong time. The very best time to dethatch a lawn is early fall, at least four weeks before the end of the summer/fall growing season. This allows grass plenty of time to grow and re-establish before frost arrives. An early fall dethatching can prepare your lawn for overseeding and fall feeding, giving it the best preparation for surviving the winter and rebounding quickly the following spring.

Late spring, after several weeks of green grass growth, is the second best time to dethatch. Of course, if you dethatched the previous fall, you won’t need to dethatch in the spring. There is virtually no thatch build-up during the winter.

If you are planning to overseed your lawn, you should plan to dethatch before seeding.

How to Dethatch – The Basics

Should You Dethatch Your Lawn?1. Choose a time when the turf is not too wet.

2. Remove twigs and other debris from the lawn

3. Mow the lawn if the grass is 3″ tall or taller

4. Attach your Dethatcher Attachment to your Mantis Tiller. Be sure to install the shields, and use eye protection. If you don’t yet have this attachment, visit the Tiller Attachments page now to learn more.

5. If this is your first time, start in an “out of the way” area until you get comfortable with how fast to run your tiller engine, and how fast to move the dethatcher backwards. Don’t worry you’ll quickly get the hang of it.

6. Clean up the thatch with a rake or bagging mower; it can be composted or used as mulch on the vegetable garden. (Add dry brown leaves now, if you have some, or later, when you can get some to help balance and speed the decomposition of your compost.) A quick final mowing, or the use of a lawn vacuum, can help remove a lot of the debris caused by dethatching.

The Final Step

Should You Dethatch Your Lawn?As soon as possible, water and feed your newly dethatched lawn. While a dethatched lawn may look somewhat ragged, you’ll be surprised and delighted at how good your lawn will look in just a few weeks.

If you’ve dethatched in the fall, now is the best time to over seed the lawn, as well. You’ll be preparing your lawn for winter survival and a quick spring recovery.

If you’ve dethatched the lawn in the late spring, you may want to apply a pre-emergent weed preventer to keep weeds from competing with your grass plants for water and nutrients.



    • Hey Constance:

      Great Question!! We do not recommend using the dethatcher On St. Augustine grass. The blades will pull all your roots right out of your the ground.St. Augustine grass is a very sensitive type of grass, therefore it is critical that the blades being used are adjustable left to right so you can put a minimum of three inches between the blades to ensure you do not permanently damage your lawn.

  1. Hello,

    I am a groundskeeper for a minor league baseball team. We had Kentucky Bluegrass put in in the fall and have been mowing almost everyday for about 2 month. Everything greened up pretty nicely but I can still see some yellow grass below the green stuff. Is it too late to remove thatch?

    • Hi Danny – we suggest dethatching during i the Spring and Fall seasons. We would be afraid of you detatching it now and risking pulling out the roots of some of your newer grass.

      Here’s some quick tips to help to decide if you need to dethatch:

      Is it bouncy? Spring? Then if so, often has a thick thatch layer.

      Visually inspect the lawn. Can you see the soil between turf crowns? If your answer is no, you’re likely looking at a thatch layer.

      We hope these tips helps! Let us know.

  2. We just had a lawn treatment the middle of August. Here a week later I would like to dethatch…is it too early for this in Iowa. Also we have damage from bugs/grubs…had grub control put down

    • We recommend dethatching in the Fall and the Spring. To determine if you lawn needs dethatching you need to visually inspect your lawn and determine you are looking at thatch layer. A thatch layer that is tough to wedge a finger through needs to be thinned. We consider a layer thicker than three-quarters of an inch a good sign it is time to dethatch.

  3. I like your advice to consider dethatching or power raking your lawn if you have cool season grass or spots where the blades are weak and farther apart. In order to determine whether it’s a good option for your yard, you’d probably want to talk to your professional lawn care service. Getting the advice of a professional could ensure that you know what services are best to keep your yard healthy and to prevent issues.

Leave a Reply

Your email address will not be published. Required fields are marked *

five × 1 =