You’ve heard about lawn thatch, right?
You’ve heard that along with aeration and other lawn maintenance chores, it’s something that needs doing from time to time.
But what causes it? And is it always bad?
Keep reading to find out everything you need to know about lawn thatch and how much is too much.
- Quick Read
- What is Lawn Thatch?
- What Causes Lawn Thatch?
- Is Lawn Thatch a Bad Thing?
- How to Optimize the Amount of Thatch in Your Lawn
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- Grass thatch is a naturally occurring component of a healthy lawn.
- It is mostly comprised of dead grass stems, surface roots and clippings.
- A layer of ½ inch or less is a good thing and important for supporting a healthy lawn.
- A layer of more than ¾ inch can be a recipe for trouble and require remediation.
No thatch at all is also a problem and can leave your lawn vulnerable to stresses.
What is Lawn Thatch?
Google “thatch” and you’ll end up with pretty pictures of English cottages with thatched roofs.
So if you’re here, you’re probably wondering, what is thatch in a lawn?
Lawn thatch is the layer of organic matter that naturally exists between the crown of the grass stems and the surface of the soil.
It is made up mostly of dead grass stems and surface roots, some clippings, and other organic matter such as small leaves that may have blown on to the lawn.
What Causes Lawn Thatch?
The accumulation of lawn thatch is a natural process. However, it is usually kept in balance as beneficial microbes in the soil break down the thatch from underneath, returning the nutrients to the ground.
Usually, assuming your soil is healthy and there are enough of these microbes present, the breaking down process will occur at roughly the same speed that the thatch accumulates, and thatch build up shouldn’t occur.
This means, in a healthy lawn that is mowed correctly, an optimum thickness of thatch should be maintained without you having to do much, or anything at all.
However, if things get a bit out of balance, then thatch can build up.
So, what causes lawn thatch to build up?
The two main things that cause lawn thatch to build up are an inadequate amount of beneficial microbes in the soil, and improper mowing habits.
Healthy soil will have a rich diversity of microorganisms present which feed on the thatch from underneath, breaking it down and returning nutrients to the soil where it can be reached by grass roots. Inadequate soil health is actually one of the main causes of lawn thatch build up.
The other thing that can cause thatch to build up is improper mowing practices. If you wait until your grass is too long to mow it, and then remove more than a third of its length AND leave the clippings on the lawn in thick clumps, then thatch is more likely to become an issue.
Leaving small quantities of short lawn clippings on the grass is actually good practice. These clippings will contribute to a healthy, thin layer of thatch without contributing to a build-up, and they will act as mulch, benefiting your grass more than a dousing of synthetic fertilizer would.
But, a large volume of long clippings is going to take much longer to break down and is definitely more likely to upset the balance.
Is Lawn Thatch a Bad Thing?
The logical conclusion would be to assume that lawn thatch is bad, and only bad. But actually, it’s all about too much of a good thing.
Lawn thatch in moderation is actually beneficial for your lawn.
You can think of it like the lawn’s own self-regulating layer of mulch.
In the right amounts, lawn thatch does multiple things to benefit the health of your lawn. These include:
- Helping to retain moisture and prevent the lawn from succumbing to heat stress.
- Helping to keep the soil warm or cool and tolerate extremes of temperature.
- Providing valuable nutrients to the soil and reducing the need for fertilizer.
Note, even though the right amount of thatch can benefit your lawn and provide valuable nutrients, if your lawn has had too thick a layer for too long, then it may actually be lacking in nutrients and need a little boost to get things back on track.
If this is the case, read my guide to the different types of lawn fertilizers before you start.
How to Optimize the Amount of Thatch in Your Lawn
So, we’ve established that the optimal amount of thatch for a healthy lawn is around ½ inch. Less than ¼ inch and things are getting sparse, more than ¾ inch and some action is needed to remove the excess.
But how do you know how much you’ve got?
The easiest way to determine how thick your thatch layer is, is to take a core sample. If you don’t have a soil corer (and let’s face it, not many people will have a corer as part of their lawn care tool kit), get a small trowel and dig up a little section of lawn, being careful to keep its structure intact.
(You can put it back where you got it from once you’ve taken your measurements.)
Use a ruler to measure the thickness of the brown layer of organic matter on the surface of the soil. Once you’ve established the thickness of your thatch, it’s time to decide what to do.
Luckily, thatch problems in lawns are easy to remedy:
Too much thatch? There are a few different ways that you can combat too much thatch in your lawn. The method you use will depend on how much thatch you need to remove and what time of year it is.
The golden rule of dethatching is that you never dethatch when the lawn is already experiencing stress in another form.
Dethatching is a form of stress in its own right, especially if you use a mechanical dethatcher. Adding another form of stress will mean it might take longer for the lawn to recover, and may even cause its health to degrade further. Most of the time, avoiding the heat of summer and the depths of winter is a safe bet.
Once you’ve picked the right time of year, you can then choose between working to increase the microbe population of your soil by feeding them with a formulated mixture from your garden store, or manually removing some of the thatch with a thin-tined, metal rake or dethatcher.
If you have a thin layer, then your lawn and soil will benefit more from avoiding the manual process and promoting microbe growth instead. If you have a thick layer then some manual removal will be necessary.
Manual removal is relatively easy with the right tools. A thin-tined metal rake works well for small areas. If you have a larger area then a mechanical dethatcher is a better option. If you don’t own a dethatcher, you can hire one.
I won’t go into detail about the process of dethatching here as I already have an excellent guide for you to read with everything you need to know about dethatching here.
Lastly, bear in mind that dethatching and aerating often go hand in hand. If your lawn has needed a good dethatching then it could likely benefit from some aeration too. I have a guide to aeration if you’re new to the process, and a list of the best aerators to use here.
Most articles about lawn thatch end up talking about dethatching and what tools and equipment are required for the job.
But what if your lawn doesn’t have any thatch? How can you help it to create this useful, protective layer?
Luckily, the answer is simple and, unlike a lot of things in life, an easy fix.
You can help your lawn to create some thatch simply by how you mow it.
First things first, take off that catcher. Grass clippings are your friend when it comes to creating some thatch. However, length matters. Set your mower to a height that will literally just take the tops off of your lawn. Think no more than ½ inch.
If your lawn is long, you’ll need to exercise some will-power and restrain yourself from whipping it all off at once. Instead, your lawn will thank you for taking it slow.
Take off ½ inch, let the clippings float happily over the lawn in a light sprinkling, wait a week, take off another ½ inch, and so on, until you have a thatch layer forming.
Hopefully, now you are familiar with the pros and cons of lawn thatch and how much is too much.
Whether you have too much or not enough, it’s relatively easy to remedy and help your lawn on its way to optimal thatch thickness.
Remember, don’t take any remedial action when your lawn is already under stress. Wait until the spring or fall, ideally when the grass is in an active growing phase.
And if you’re feeling overwhelmed by all the potential jobs that your lawn requires, fear not, I have a lawn care calendar here to help guide you through the year and remind you when to consider carrying out each task.
As always, please let me know your thoughts in the comments section below and share with anyone who might find this useful too!