Biological Liquid Dethatcher for Lawns – Do They Work?

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Robert Pavlis

Biological liquid dethatcher for lawns is a new category of product that makes it very easy to eliminate thatch from your lawn. You no longer need to use special thatch rakes or rent motorized dethatchers to clean up your lawn. Just buy a bottle of liquid dethatcher, mix it with water and spray on your lawn. Some products even incorporate fertilizer combining two jobs into one.

How well do these products work? Are liquid dethatchers more efficient than traditional mechanical dethatchers? What is thatch anyway and is it a real problem?

Biological Liquid Dethatcher for Lawns - Do They Work?
Biological Liquid Dethatcher for Lawns – Do They Work?

What is Lawn Thatch?

I have written about lawn thatch before in, Dethatching Lawn Thatch.

In summary, thatch is a layer between the lawn and soil made up of mostly grass rhizomes and roots, much of it dead. It can build up over time and once the layer gets more than about 1/2″ thick, it is a good idea to remove it.

Something many people don’t know is that a thatch layer of less than 1/2″ is actually good for your lawn. See the above link for more details.

Compost Science for Gardeners by Robert Pavlis

Before you think about using a biological liquid dethatcher, check your lawn. Most people do NOT have a thatch problem.

Traditional Dethatchers

Lawn dethatcher, photo credit: John's Home & Yard Services
Lawn dethatcher, photo credit: John’s Home & Yard Services

According to the Ohio State University power dethatchers and power rakes work very well. Dethaching attachments for lawn mowers do not work. Manual raking can remove thatch but it also does a lot of damage to the lawn.

The best traditional way to reduce thatch is core aeration.

Does Core Aeration Work?

Core aeration is also recommended for reducing thatch and it might help a bit, but the scientific evidence for this is poor.

What is a Biological Liquid Dethatcher?

The main ingredient in these products is a mixture of bacteria. Thatch decomposes naturally through the action of bacteria. It then follows that too much thatch indicates a lack of bacteria, so these products add more.

One product also contains something they call a carbonic enzymes, without specifying which ones. If you search for this term, it identifies a family of enzymes called Carbonic anhydrases, which “assists rapid inter-conversion of carbon dioxide and water into carbonic acid, protons and bicarbonate ions”. I see no connection between this reaction and the decomposition of thatch, and the manufacturer provides no explanation in their marketing material.

The Science on Liquid Dethatchers

The website of almost every product I looked at made the claim that “science has shown liquid dethatchers work”. If that is true, its odd that not one of them provides a link to this existing science.

So I went looking for the science. Unfortunately, I did not find much, but I did find one review, “Application of active culture, like most biological control methods, has not been proven sustainable under field conditions.”

Another study looked at the effect of biological dethatchers containing fungal species and found no reduction in thatch.

This is not a hot scientific topic. Thinking that I might have missed the studies, I sent an email to every manufacturer I could find – to be honest there are not that many. I asked them, “I have never heard of a liquid dethatcher. Can you please provide some links to scientific studies that show it really reduces thatch”. I only got one reply, and they were unable to send any study, but they did assure me that their product worked.

Clearly, the science does not support the idea that liquid dethatchers work.

Frequency of Application

Commercial products recommend that the product be applied repeatedly. One brand says, “For heavy thatch conditions, use 3 oz per 1000 square feet every three weeks.”

If bacteria are added to the lawn and they thrived by decomposing the thatch, why would you need to reapply them? Bacteria living in a suitable environment, with lots of thatch food, would continue to prosper until the food source was gone. If this product worked you should not need to reapply in the same season.

Will Adding Bacteria Help Reduce Thatch?

We know that bacteria decomposes thatch, so adding more would seem to make sense. But there is a flaw in this logic.

The amount of bacteria added by any product is extremely small compared to the natural population already there. The bacteria you add will not decompose even a few roots. For this to work, the added bacteria need to multiply to create huge populations of active bacteria.

The great thing about bacteria is that they can do this if conditions are right. In a lab, some bacteria divide ever 20 minutes, producing millions in a day. For this to happen they need suitable environmental conditions and lots of food.

If those things existed in the lawn, the native bacteria would have already grown in numbers and taken care of the problem. That did not happen because conditions were not right for it to happen. Adding a few more bacteria will not change that.

You might think that the bacteria you buy are special, but they aren’t. The bacteria that decompose thatch are already in the soil and on the grass.

Simply adding bacteria will not get rid of thatch.

How Do You Stop Liquid Dethatchers?

Lets say I am wrong and liquid dethatchers work. You add the microbes to the lawn and they start decomposing the thatch. Things are looking good. Your 1.5″ of thatch is slowly getting less with each passing day.

Things are going so good that the thatch layer is now at the 1/2″ mark. You don’t want the layer to get any less because that is not good for the lawn. How do you stop the microbes?

If they were GMO microbes they might be smart enough to stop on their own, but these are just natural microbes. They don’t know enough to stop.

I think you can see that even if these products worked, the idea that they would produce a healthy lawn is flawed.

DIY Liquid Dethatchers

Several DIY formulations are also presented on the net. They generally include soap, sugar or molasses and maybe a beer. Other ingredients include mouthwash, soda pop and ammonia. You can even get a ” Secret Lawn Tonic Recipe From Golf Course Groundskeeper”, which controls thatch.

I don’t normally promote home remedies, but this one might work. The idea is to stimulate the natural bacteria in the soil to grow faster and multiply. This larger population will then be more active and digest the thatch. There is some science to support this idea. Adding a food source (sugar) or a nitrogen (ammonia) source does seem to reduce thatch.

The beer and pop are just expensive sources of sugar. The mouthwash will probably kill bacteria – not sure why it is used. Soap is always added to every DIY formulation to make it stick to things.

One problem with this approach is that you need to add a lot of sugar, much more than most DIY recipes suggest. Once the sugar is used up, the microbe population will crash and you are back to square one.

What to Do With Too Much Thatch

Poor soil has fewer microbes which allows thatch to build up. Any practice that improves soil health will help reduce thatch. The following work; add more organic matter. prevent compaction, water adequately, keep fertilizer application to a minimum and perform core aeration.

A soil pH of less than 5.5 reduces microbe activity and leads to more thatch. In this case liming will help.

Top dressing with sand may reduce thatch.

Improve soil health and the bacteria population will naturally increase and take care of your thatch problem.

If you have a severe thatch problem, use mechanical removal to get ahead of the problem, and then use the above suggestions to maintain a lower level going forward.

Other Articles About Lawns

How to Get Rid of Moss in Lawns

How Long Does Grass Seed Take to Grow?

The Truth About Clover in the Lawn

How To Add The Right Clover To Your Lawn


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Robert Pavlis

I have been gardening my whole life and have a science background. Besides writing and speaking about gardening, I own and operate a 6 acre private garden called Aspen Grove Gardens which now has over 3,000 perennials, grasses, shrubs and trees. Yes--I am a plantaholic!

18 thoughts on “Biological Liquid Dethatcher for Lawns – Do They Work?”

  1. I recently started taking care of a lawn that had been just minimally cared for. After I got the St Augustine growing well again I had to deal with some large thatch areas, some up to 1-1/2 to 2 inch’s. I started applying micros and other soil improvers. I found a product by Green county fertilizer called d-thatch. It’s enzymes some humic, molasses and yeast. A few weeks after I had applied it the deepest thatch was turning to mush. The St Augustine started growing stolens across the bare spots that were just thick layers of compacted dead grass. I did a second spot application on these heavy spots. After a couple more weeks and some good rains the thatch layer was turning to mush. I’m hoping that this will continue, I’ve started finding earthworm casting piles in these spots. Everywhere the earthworms had left a small pile the stolens were rooting in place. If this continues through the fall and I can start it going well next spring it should be down to a healthy layer. Seems lots of things like broken down sugary thatch. At 1% sugar it’s just a taste to get things moving. After two sprays, one broadcast and one spot treatment, it’s made some good progress. I didn’t want to mechanically de-thatch because I wanted all the nutrition that’s in the thatch and the carbon it contains to go back into the soil.

  2. Lived in community of 280 hmese where the developer used Centipede on 90% of the lawns. Most people lost their lawns after years. I read where Centipede likes lower ph so I kept mine around 6.0 max. Our lawn did start to show signs of dying and my wife found liquid dethatcher. We added it and lawn came back. You must water enough to reach all thatch. We kept applying it twice a year and had best lawn in neighborhood until we moved 13 years after starting liquid dethatcher. If it ain’t broke, don’t fix it so we kept using it.

  3. Well shoot ! I’m so disappointed to read this! This 76 yr old woman was excited about an easy way to dethatch .Back to the drawing board.

  4. It looks like I used too much liquid dethatcher on my new sod. It is now bare of thatch and not looking too healthy. Should I just add more fertilizer to try and bring it back?
    Or is there something else to slow down the bacteria?

    • I don’t follow. New sod does not have thatch and does not need to be treated.

      Too much dethatcher will harm sod, but it is the excess nutrients that burn it – not the microbes. Excess bacteria simply die.

  5. I read a lot of negatives about various fertilizers and gardening techniques from you . I do not hear many alternatives or better ideas so what are we supposed to do . Your article on thatch eating microbes sounds right but you only suggest mechanical alternative but you stop short at saying this is the only method that works . I like to read your articles but I also want to know what does work in gardening as apposed to what does not .


  6. John,
    I’m with you, I love manually dethatching, however, I have a very large yard now and I am 59, and it’s hurting my back. I have been researching the liquid dethatchers and I really don’t care about the science of it all, I just need any help I can get

    I do read reviews and I leave reviews. To me, they are mostly telling.

    I am going to try the liquid dethatchers. Who knows the next article I read may scientifically endorse the liquid!!!

  7. Used a granular dethatcher from a company in east Texas but it’s been so long ago I can’t remember the name of the product or company. That stuff was fantastic. Sprinkle on the lawn before a little rain and a few days later the thatch was gone.

    • Thatch would not disappear in a couple of days. It would need to decompose for it to disappear and that would take weeks.

    • Yes – that is one of the products that fits into the post – no science it works.

      Positive reviews mean nothing – they are not left by scientists.

      • I personally think proven science is only proven until better technology or better science disproves the previous science. Meaning, the old science was not factual in many cases. I only say that because you have to see what works for you. There are many times I hear the “science proves this” and then they will say in the 10 studies they did. Science and Stats are just ways to get you close or a foundational starting point.,.,most of the time it’s not a FACT. just my opinion.

        • Science does not prove anything, but it gives an indication of current thinking. When that thinking and data does not change over time, the results are more strongly believed.

          But that is the best we have. If one disagrees with the current thinking, and has no better science to support their position, their view is just that – a point of view with no basis.

  8. Great post! And something I’ve never heard of.

    Yes. I have thatch! Every other year (odd years), I power rake & run the slicer dethatcher in even years. (It’s fun, I like doing it, and I Love the challenge of removing dead grass from sharp prongs!)

    About every third year, I have enough Compost (the stage well past leaf mulch) which I cover the trouble areas of my lawn and reseed.

    Compost adds (dumps) a lot of bacteria, worms, and worm castings! And, I think” far more than any bottled bacteria or “home remedies” will ever provide.

    Sure – some might call it “work,” but for this 75 year old, it’s Pure FUN!


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