When I am preparing my turf of St. Augustine grass for speedy summer growth, I go through a little checklist. One box on my list is always to check the thickness of the thatch layer. I like to think of thatch as our lawns plaque and dethatching as a yearly trip to the dentist.
While a thin layer of thatch no more than ½ inch high is harmless and even useful for soil microbes, too much thatch can kill a stolon propagating grass like St. Augustine. The dead plant material that makes up thatch absorbs water, prevents nutrients from reaching grass roots, and blocks the grass’ runners from replanting themselves and spreading.
Knowing that thatch build-up can be harmful means we need to look at what steps we can take to reduce and prevent it from getting worse. We will look at whether it’s safe to dethatch St. Augustine and, if so, what to do and not to do when controlling this issue.
Is it OK to Dethatch St. Augustine Grass?
Using a dethatching rake or a hand rake, it is OK to dethatch St. Augustine grass. It is also OK to use a vertical mower with the blade set 3” apart to dethatch St. Augustine grass. Make sure only to make one pass with the mower, or you could irrevocably damage the turf.
Many lawn grasses spread by runners and by rhizomes, making it safe to mow short or use a power rake to dethatch. When these turfs are dethatched using a dethatching machine, aka power rake, they can grow back from the rhizomes even if the runners were destroyed with the thatch.
St. Augustine only propagates via stolons or runners that punch down into the soil and reroot. This growth pattern allows it to fill in large patches quickly and gives it the thick matting quality we all love. If you dethatch with a power rake, you will kill your St. Augustine grass and need to completely resod or reseed your yard.
Without the rhizome propagation abilities of other turfs, St, Augustine can be decimated if dethatched with a power rake or dethatcher. Too many of the stolons will be destroyed for the grass to recover. This will lead to dead patches and a lawn susceptible to disease and infestation.
Frustratingly, too much thatch can kill your turf, but so can aggressive thatch removal. It is a delicate line that a lawn owner must walk to properly maintain their turf without overdoing it to the point of detriment. Let’s look at when and how to dethatch St. Augustine grass.
When Should I Dethatch My St. Augustine Grass?
After winter dormancy, the spring is when you should dethatch St. Augustine grass. This is necessary only if the thatch layer is ½” thick or thicker. If you dethatch in the late summer or fall, the grass will be too close to its dormant period to recover. It is important to wait until the turf is tall enough to cut before attempting to dethatch, usually by mid to late March.
You may also want to consider the weather and yard conditions before dethatching. Removing the thick mat of dead plant material will damage your turf and cause great stress. You will want to choose a time to dethatch with these factors in mind.
The level of moisture in your soil will also affect your turf’s recovery from dethatching. If the soil is too dry, the dethatching rake will pull up everything as one large mat. If the lawn is too wet, you will likewise pull up whole patches of turf by the root, and you create an ideal environment for pests and fungus in your grass.
How to Dethatch St. Augustine Grass
There are two effective ways to dethatch St. Augustine Grass. You can manually remove it with a dethatching rake or hand rake if your yard is 1,500 Sqft or smaller. If you have a larger yard, you will want to use a vertical mower for deep thatch layer removal.
Regardless of which of the two dethatching methods you choose above, you will need to do some preparation to ensure a swift recovery for your St. Augustine grass. Follow the steps below to find out how to dethatch St. Augustine grass.
St. Augustine prefers a height of 3 to 4 inches as it allows the runners’ room to split off and restem in the soil. Dethatching is best done with low-cut grass to ensure the blades and tines catch as much dead material under the living grass as possible. If St. Augustine is cut below 1 ½ inches, it will unlikely survive dethatching.
Mowing the turf to 2 inches about 24 hours before the dethatching allows the tools to be effective without killing off the grass. Make sure to collect the grass clippings if you usually let them drop, as the debris will only mean more work during dethatching.
As was mentioned earlier, the proper moisture level can make dethatching more effective. After mowing, make sure to water the grass so that the soil is moist but not damp. Watering beforehand will help the thatch dislodge easier and will aid in the recovery of the grass. Once the thatch is removed, the soil and roots will have access to much more water.
If you are using a hand rake or dethatching rake, all you need to do is repeatedly pull against the thatch at the soil level. Use short movements to keep the thatch together as you pull it over and past the turf. Repeat until you have removed as much thatch as possible and compost or dispose of the waste.
If you are using a vertical mower, you will need to set the blades 3 inches apart. Make sure to only make a single pass over the yard and do not mow any areas twice. While still more aggressive than the dethatching rake, if done correctly, you should have removed all of the thatch without causing too much damage to the St. Augustine grass.
Once the turf has been dethatched, you can immediately begin taking steps to avoid future build-ups. Using a core aerator go over your lawn and properly perforate the newly exposed soil. Doing this right now will prepare your soil for better water, fertilizer, and herbicide absorption and yield your lushest lawn yet.
Even the gentler methods of dethatching can be stressful to your lawn. It is important to give you grass the best start to recovery possible. Adding fertilizer with equal parts nitrogen, phosphorus, and potassium is a good way to jumpstart growth.
The bare patches and exposed soil left from dethatching are the perfect places for broadleaf weeds to thrive. It would be a shame for you to do all that work only to have your lawn overtaken by weeds and not St. Augustine. Laying down a pre-emergent herbicide will ensure that your turf will have no competition as it burst into the summer growing season.
What Causes Thatch?
Some common causes of thatch are grass clippings, yard debris, compacted soil, and shallow watering practices. All of these factors add up and cause the helpful soil decomposition layer to become a suffocating mat.
Most lawns need to be dethatched annually or every other year to properly mitigate turf damage. If you live in a climate that requires more cutting, you do not bag your cuttings, or you have additional landscaping that adds more leaf litter, you may need to dethatch more frequently.
How to Prevent Thatch?
There are a few ways to prevent thatch and to make sure that your turf can flourish with minimal interference. Mowing your St. Augustine to a minimum height of 4 inches will decrease the number of grass clippings that become thatch.
Bagging your clippings or occasionally hand raking can also reduce the frequency that dethatching will be needed. The most important thing you can do to prevent thatch is to add a deep, irregular irrigation day once a week.
Choose any of your watering days during the week and adjust your soak time to a full 45 mins. This will aid in the rapid decomposition of the thatch and prevent it from building up above the maximum ½-inch level. Keeping thatch under control like this will promote soil health and give your turf a critical boost.