Did you know there's a debate in the lawn care space about whether you should dethatch St. Augustine grass? And really, that's probably why you're reading this article right now.
Can you dethatch St. Augustine grass? Should you dethatch your St. Augustine lawn?
If so, what's the best way to dethatch St. Augustine grass?
We'll answer all of those questions—plus lots more—in this guide.
Bottom line: you can dethatch St. Augustine turf. But you probably shouldn't have to. And if you do have to, make sure you do it the right way.
Let's jump to it.
Can You Dethatch St. Augustine Grass?
Yes, you can dethatch St. Augustine grass. You can dethatch any grass you want to!
The better question is: should you dethatch it?
Now, to be clear, lawn thatch can be a real problem. In fact, a thick layer of thatch can be a breeding ground for insects and disease-causing organisms, while creating an impenetrable barrier to allowing air and water into your grass and soil. And so removing that thatch has many benefits.
But here's the thing: St. Augustine grass lawns don’t typically have a "thatch problem". They're spongy and thick by nature, which some homeowners mistakenly identify as "thatch".
Before you decide to dethatch your St. Augustine grass, go out and actually take a look at your lawn! Dig up a couple of small patches, and see if you actually have a thatch problem.
Is the grass growing on the soil? If yes, you're fine. Is the grass growing on a thick thatch layer? Ok, let's look a little bit closer.
If the thatch is less than ½ inch thick, you do NOT want to dethatch it! If the thatch is 3/4 of an inch or larger, then yes—you should dethatch it.
Reasons To NOT Dethatch St. Augustine Grass
St. Augustine grass doesn't usually require dethatching because of the way that it grows. It spreads by way of stolons (above-ground runners), crawling along the surface of the soil, growing roots, and sprouting blades of grass.
If you dethatch it with a power rake or scarifier, you'll risk removing a lot of the top growth—this is how it spreads and fills in bare patches of soil. It's important to understand that there are both pros and cons to dethatching.
Another thing to note is most professionals recommend mowing your lawn to 1" after dethatching, but St. Augustine grass doesn't thrive if it's cut under 2.5”. So when you combine removing a lot of top growth plus mowing the grass to 1”, your St. Augustine lawn will probably not make it.
That said, the act of "dethatching" is simply removing thatch. It's the method of doing so that you have to be cautious about! It's especially important to NOT use a power rake when dethatching a St. Augustine lawn because it can severely damage the roots. We'll examine other methods for doing so later in this article.
What Is Thatch And What Causes It In St. Augustine Grass?
Thatch is a layer of undecomposed organic matter and dead plant material (stolons, roots, crowns) intermingled with live plant stems at the soil surface.
Note that leaving dead grass clippings on the surface after mowing does not cause thatch buildup, because clippings are readily broken down by microbes in the soil.
Thick thatch develops when you overfertilize, overwater, or improperly mow your lawn. And too much thatch can stunt root growth, become a safe haven for insects and disease, and make pesticides less effective.
An excessive thatch layer reduces water penetration and can bind fertilizer or pesticides. In severe cases, roots may be seen actually growing above ground and rooting into the thatch layer.
Obviously, this isn't good for your lawn and should be addressed asap.
The thing about St. Augustine grass in particular is that it's prone to excessive thatch buildup when you hit it with a lot of nitrogen fertilizer and you irrigate frequently.
When Should You Dethatch St. Augustine Grass?
When should you dethatch your St. Augustine grass? You should dethatch your St. Augustine grass in late-Spring. This is the period when your lawn is growing most vigorously, as it needs time to recover from the dethatching process.
You can check how thick your thatch layer is by cutting out a piece of turfgrass in your lawn with a shovel. Examine the soil beneath the grass leaves.
The thatch layer is a brown color, and you'll notice it looks different than the soil below it. If the thatch layer is thicker than 3∕4 of an inch, it's time to dethatch!
You shouldn't have to dethatch your lawn more than once per year, max. And you shouldn't dethatch your lawn when it's overly wet or after it rains.
Prepping Your St. Augustine For Dethatching
Before you start the dethatching process, you should prep by grass by doing the following.
Water your grass the day before
You'll definitely want to water your grass the day before dethatching it, especially if you have a thick layer of thatch on your St. Augustine lawn.
The point of watering is that it helps the lawn recover faster from the stress caused by the dethatching.
Quick watering tip: you want damp soil, not a pool of mud.
Mow your lawn
You'll also want to mow your lawn before you dethatch it. We recommend mowing your St. Augustine to 2.5 inches.
This allows your dethatching tool of choice to more easily get to the thatch lawyer below the grass blades, without removing too many of the stolons.
How To Dethatch St. Augustine Grass
We recommend two different methods of dethatching your St. Augustine grass.
The first is with an electric dethatching machine. This method is cheaper, less laborious, and you're less likely to mess up your lawn. The downside is it doesn't do quite as extensive job as your second option.
Your other option is to use a verticutting machine. These are big, powerful machines that do a wonderful job. But if you don't know what you're doing, you can cause some serious damage to your lawn.
Let's explore these options in more detail.
Use An Electric Dethatching Machine
A dethatching machine operates much like a push lawn mower. You run it up and down your lawn, and it works to dethatch your lawn. We recommend the Greenworks 10 for the job, with its 18 tines, which are 14-inches each (and adjustable).
What we love about this machine is that it's an affordable way to dethatch a big lawn. You can purchase it at big box retailers for around just $80, and it has the capacity to dethatch lawns as big as 10,000 sq. feet.
The way it works is you simply hold down the handle bar, press the power button, and walk slowly behind the machine, as if you were pushing a mower.
The 18 tines then get into action, grabbing and pulling up the dead grass and thatch, propelling the machine forward. The thatch is pushed out of the back of the machine. To stop the machine, simply let go of the handle.
To dethatch with an electric machine like the Greenworks 10, it's best to move in a straight line. It's not a machine that does well with turns and maneuverability. When it's time to "turn around", simply stop the machine, and turn it around for the next row.
One thing to be aware of with an electric machine like the Greenworks 10 is that it requires a power cord—a big, durable, 100-foot power cord.
Because of the cord, you have to be careful when operating the machine not to accidentally cut the machine when you're dethatching! You'll also have to maneuver around any bushes, shrubs, and trees in your lawn, since the cord is tethered to the machine.
Bottom line: the Greenworks 10 is easy to assemble, lightweight (lighter than a gas-powered push-mower), a great bang for your buck, and works on large yards. The only thing to be aware of is you're going to need a heavy duty extension cord to operate it.
User A Verticutting Machine
Another option is to rent a verticutter machine. You can typically rent these for a day from your local hardware shop. For example, this one rents out at $88 for the day (which, we should note, is more than the cost to buy the Greenworks 10).
Verticutters are powerful machines that do a more thorough job of dethatching than an electrical machine, but they can cause serious damage to your lawn in the wrong hands.
Verticutting machines use vertical blades that slice agressively through the heavy thatch layer, removing the dead material from your lawn. Most professionals recommend using a 3-inch spacing distance between the verticutter blades for St. Augustine grass.
There are a couple of precautions you should be aware of when using a verticutter.
One, these guys do a number on your lawn—so your turf will need a long period of time to bounce back. Becauase of that, it's imperative to do your dethatching when the grass is most actively growing.
Two, you should only operate the machine in either an east-to-west, or north-to-south pattern—but not in all four directions, as that will resk over-thatching your yard.
Three, spacing and measurements are important. As we mentioned, you should use a 3-inch spacing distance between your blades, which is much wider than spacing that you'd use for Bermudagrass, for example.
The blades should also be set to where they are not penetrating the soil surface. You want about 1/2 inch of space between the bottom of the blade and the top of the soil. .
While verticutters are an effective tool for the job, we find they're not quite practical for your average homeowner. For one, you have to go to the store to rent it—and go back to return it, which is a huge time-suck. For two, a single-day rental is more than the cost of purchasing an electrical machine. For three, if you don't know what you're doing, you're going to ruin your grass—these machines are usually best left for the professionals.
Dethatching Precautions To Take
The most important precaution to take when dethatching St. Augustine lawns is to NOT use a power rake! They wreak havoc on the stolons and ruin any chance of a decent recovery.
Power rakes are extremely aggressive and powerful, and they will not only remove the thatch from your lawn but the grass stolons as well—which can cause great damage to your lawn!
Stolons (above-ground runners) are especially important for St. Augustine grass because that's the only way it grows and spreads, whereas other types of turfgrasses utilize both stolons and rhizomes (underground).
What To Do After Dethatching
What should you do with the thatch after you're done dethatching?
Immediately after dethatching, you're going to want to remove it from your lawn. You can either rake or vacuum it away for composting, but definitely don't leave it on your lawn.
About a week after dethatching your St. Augustine, you can apply fertilizer to your lawn—about 1/2 a pound of nitrogen for every 1,000 square feet to spur recovery. The fertilizer should be watered into your soil to prevent your grass from burning.
If you want to take it one step further, you can topdress your lawn by adding a uniform layer of soil on top of your grass, which should help with future thatch buildup. Just be sure to use a soil that doesn't contain weed seeds, and always follow the recommended amounts.
How Often Should You Dethatch St Augustine Grass?
You'll find that every St. Augustine lawn is different, with some needing to be dethatched every year, while others only need it done every other year. Always be sure to diagnose ahead of time by measuring the amount of thatch buildup in your lawn.