Almost all healthy lawns that are well looked after will develop thatch over time. The amount of thatch will vary with each different lawn, the lawn type which is being grown, and other environmental factors such as shade levels or direct sunlight levels, how much fertilizer is applied to the lawn, how often the lawn is mowed etc. These variables which lead to a build up of lawn thatch are endless.
Thatch is a normal and a healthy aspect of all lawns, as it gives the lawn a cushioning under foot, as well as protecting the soil and lawn roots from evaporative water loss. The thatch layer is made up of grass runners, both alive and dead, lawn leaf, and some other organic matter which may be lodged amongst it as well. And as far as Saint Augustine lawns go in particular, the above ground runners pretty much make up the entirety of the lawn anyway, almost equally as much as the green leaf of the lawn.
Thatch however can become a problem when it increases too much, when there are just too many Saint Augustine grass runners that just keep growing thicker and thicker on top of each other, which is most prevalent when a Saint Augustine lawn is grown in full sun conditions. Other lawn types such as Bermudagrass will thatch up very quickly and will need to be remedied every so often, while the same can be said for Zoysiagrass lawns as well.
If our lawn is becoming quite spongy underfoot, no matter the lawn type, then it may be worthwhile considering cutting back some of that thatch every year or even once every few years.
Without cutting back the thatch of such a lawn, the thatch will only increase in thickness and severity each year, leading to more problems such as scalping lawns when mowing for an example.
Cutting Back Lawn Thatch In Spring
Spring as we know is when lawns begin to jump back to life and growth again after a long cold Winter. The temperatures are still fairly mild for most of us in the early Spring, with lawn growth rates slowly increasing as each day passes to take us closer and closer to Summer, when our lawns will experience full growth rates provided they are being watered and cared for properly.
This makes Spring the perfect time to cut back the thatch layer in our lawns, as there is no risk of sun or heat damage to the now vulnerable lawn, and with the turf actively growing it also means repairing from our maintenance should be quite easy and quick too.
De-thatching a lawn in Fall can risk the lawn going into Winter being damaged if it goes into dormancy too soon after our work, while de-thatching in Summer can lead to the lawn being sunburnt, dried out and heat damaged should a heat-wave arrive, which could take a very long time to repair from that further damage. And this is what makes Spring the very best time possible to de-thatch our lawns.
De-thatching Our Lawn With A Lawn Mower
All warm season lawns such as Bermudagrass, Saint Augustine, and Zoysiagrass can all be cut right back with a rotary lawn mower to help de-thatch the lawn.
Special consideration should be given when de-thatching a Saint Augustine lawn as this lawn type does not have underground runners (rhizomes) from which to help repair itself after de-thatching, so be sure not to cut back too low on a Saint Augustine lawn, and be sure the weather is still mild when doing this work.
The basic premise that we want to achieve here is to remove a lot more of the top layer of the lawn than we normally would when mowing our lawns at regular heights. We want to bite into the thatch layer and SCALP the lawn. This is why we don’t de-thatch lawns with a lawn mower in Summer as the lawn will become very burnt very quickly, though professional verti-mowing to de-thatch lawns can be done in Summer.
The safest way for the homeowner to achieve this scalping of the lawn to remove a buildup of excess thatch is to do so slowly over several lawn mowings.
Let’s imagine that we mow our lawn on Number 6 height on our particular lawn mower, and that this is the perfect height for how we like to keep our lawns.
The first mowing to cut back thatch then might be to simply go one notch lower to Number 5.
Now instead of perhaps leaving the lawn for the normal say 3 weeks between mowing in Spring, we might mow the lawn next after 7 or 10 days. And next time we might go down one notch lower again on the lawn mower and cut the lawn at Number 4.
We can repeat that same cut height at the next lawn mowing again after 7 - 10 days if we wanted to, and if the lawn continues to look as if it may still be recovering from the last cut at Number 4. So if the lawn isn’t looking the best, cut again at Number 4, very simple.
After another 7 - 10 days have elapsed, and if the lawn is looking better and greener from the last one or two mowings at Number 4, then we could go down another notch to Number 3 on the lawn mower if we so choose, though it may or may not be necessary for your own lawn. Only you can decide what is best for your lawn and to judge for yourself the condition of your lawn, and to adjust lawn mowing practices as is best suited.
So let’s say we’ve gone down to Number 3, what now?
Well, we could cut another one or two times at that same Number 3 height if we wanted to try to remove a little more thatch, or perhaps just the one cut at Number 3 height may have been enough? Determine what is best for your lawn and how you would like to proceed. A second cut at the lower height can be beneficial to cut back just a little more thatch.
Likewise if we wanted to go lower still on the lawn mower, we could, but just be careful not to go too low, there’s no need to go back to bare soil or anywhere near it, we still want some thatch and green leafy lawn showing at all times so as to be as safe as possible with our lawns.
Once we’ve removed all the thatch we want from our lawns, we let them grow back to our normal preferred growing height after that, and then resume mowing at our regular Number 6 mowing height if that’s the height we originally preferred.
Excess thatch should now be removed, and we should have a lot more green leaf to our lawn.
We can of course be more aggressive with the scalping and de-thatching of our lawns, though this of course comes with a higher risk when we remove more thatch at any single lawn mowing. This article was written in such a way so the homeowner could de-thatch their own lawns with their regular rotary lawn mower with the highest safety for the lawn and confidence for the lawn owner.