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What really is thatch?

Discussion in 'Lawn Mowing' started by GroundKprs, Nov 30, 2001.

  1. GroundKprs

    GroundKprs LawnSite Bronze Member
    Posts: 1,969

    Sorry, I still can't get time to study this @#%!^ digital camera, but here's a try.

    We all have looked down on a lawn and seen the blonde laid down blades of grass. Many refer to this as thatch, but this is not real thatch, but just dead or dormant blades. A "dethatching" of this type of lawn will often result in tremendous amounts of fluff, and many people think they have preformed a useful function by removing all this debris from the turf. But in fact this is mostly just dead grass blades that would soon decay to nothing. (The average bluegrass leaf lives 4 to 6 weeks, then it dies and is replaced by new leaves.)

    If you go to a doctor with a runny nose, does he just look at your nose and prescribe a remedy? Of course not, because the runny nose is just a symptom; the doctor will look inside, perhaps even take blood tests to determine the problem. Likewise problems you see on a lawn surface are usually symptoms, and you must look in the proper manner for the actual problem. And where is the grass growing? In the soil. So you must look below ground to accurately assess plant vitality and many plant problems.


    There are a number of ways to look underground without destroying a lawn:
    - The soil probe ($20 to $30) is a quick way to get a look, but the small diameter of a probe tends to destroy the real soil profile. But this is a most basic tool, for it allows a quick look in various places. Also in time, you will learn to detect thick thatch and compacted soils just by pushing the probe into the soil.
    - A spade will allow you to cut a triangular or square section of turf, up to 4-5 inches deep, but removing this plug is sometimes a little destructive to the plug.
    - A cup cutter is a very good tool for sampling and diagnosing. And it is not destructive of the turf. You can pull out up to a 6" deep plug, completely intact. It is also a neat sample to send into diagnostic labs for detailed analysis (and a good way for Jim to take a problem to a good friend to analyze, instead of imposing on him to come to the site). But I suppose a decent cup cutter these days is $200 to $400, so don't rush out to buy one. Start with the probe and spade; get a cup cutter later to save yourself time and effort.


    Turf Medic likes this.
  2. GroundKprs

    GroundKprs LawnSite Bronze Member
    Posts: 1,969

    "Thatch is a tightly intermingled organic layer of dead and living shoots, stems, and roots that accumulate just above the soil surface." So you have to look under the surface to determine if you have a thatch problem.


    In the pic, the soil shows up as black, and a little shiny. Between the surface and the soil is the thatch, hopefully somewhat brownish to you in this pic. This lawn does have a problem, because thatch is 1" thick.

    But the thatch is tightly packed dead stems, roots, and maybe even fine tree roots. If you think of a 1" thick woolen blanket, you have a good picture. The thatch will tear easier than the blanket, but you will not remove much of this with any type of scratching tool. You can run your JRCO "dethatcher" over this lawn 50 times, then pull a plug and you will still have 1" of thatch. Now if you have a completely dead, heavily thatched lawn area, that has been sitting that way for several months, and no new vegetation has started to grow, you might have some luck with a tine-type machine by pulling the thatch loose from the soil (like hooking the throw rug with your toe); but you will have a lot of pieces, and whole sections, that you will have to cut away somehow.

    To remove thatch as pictured above, you are going to remove most of the grass growing also, so true thatch removal is a very destructive process. Ask the southern guys who have to do St Augustine regularly. If you determine that thatch must be removed, as the Purdue document suggests, a sod cutter for 1" or more, or a powerrake with fixed vertical blades is the proper way to go. The powerrake will have to be run over the renovation area at least twice, up to 4-5 times, with blades cutting through the thatch into the soil. As you cut in different directions, you are cutting the thatch into smaller pieces, and they begin to break loose from the soil.

    Some grasses are predisposed to thatch production, but proper management can control it. I have corrected a 1-3/4" (yes one and three quarter inches) thatch problem by four years of twice annual aeration, each aeration being four passes. And others are controlled by aeration, but proper aeration is another story.

    <a href="http://www.agry.purdue.edu/turf/pubs/ay8.htm">Purdue document, includes thatch (html)</a>
    <a href="http://www.agry.purdue.edu/turf/pubs/ay-8.pdf">same Purdue document (pdf)</a>

    If anyone has questions, post and be patient. I might not be back for a couple of days. Carol just set the sledge hammer next to the computer, and gently reminded me that the Christmas decorations have to be done (anyone else have even the bathroom decorated for Christmas?)

    underground profile.jpg
  3. andyslawns

    andyslawns LawnSite Member
    Posts: 83

    are you gonna have this published or something??....... Good reading. thanks for the (detailed) info.:blob4:
  4. awm

    awm LawnSite Gold Member
    Posts: 3,354

    couldnt have said better myself. in fact couldnt have said it half as well . good answer groundskeprs
  5. KirbysLawn

    KirbysLawn Millenium Member
    Posts: 3,486

    Ain't that the truth. VEry good and informative post as usual! I guess I will have to take the dethatcher I got from Home Cheapo back tomorrow.:mad:
  6. Turfdude

    Turfdude LawnSite Bronze Member
    Posts: 1,900

    Excellent Post!!!

    My warden also has my W.E. booked w/ Christmas lights, breakfast w/ Kids & SANTA, etc. The woman is a fanatic w/ this holiday!! Every room (both baths included) get decorated. Probably 75 or so Dickens Carolers, and a plethora of other junk. The neighbor,s simply call me Clark (GRIZWOLD) for the next month or so.:rolleyes:
  7. Guido

    Guido LawnSite Silver Member
    Posts: 2,085

    Good reading for all!
  8. GroundKprs

    GroundKprs LawnSite Bronze Member
    Posts: 1,969

    When you have time, could a moderator please replace the image in that post with this image, and then delete this post please?

    Jim I edited as you asked, I left this post since it has the hyperlink to the attached photo.


  9. bastalker

    bastalker LawnSite Senior Member
    Posts: 965

    Grndskeeper.....awsome post.. I had to bring it up again since I just landed a new client who wants his yard dethached....

    He wants dethatching done to grub areas...probably half his yard.
    Was going to go nuts with a rake to these areas since its not the whole yard...Maybe half of the back yard.

    He then wants a 1 ton lyme spread on his lawn..gettin moss he is.

    What would be the quickest way to get these areas dethatched and what would you charge to do it?

    Gotta get back to him in a couple of days...
  10. GroundKprs

    GroundKprs LawnSite Bronze Member
    Posts: 1,969

    Depends on the size of the area. Generally a sod cutter is the easiest, especially if lawn is mostly dead. Cutting thatch away with sod cutter results in smallest volume. Say you have 1000 ft² with thatch 1" thick; that is 3 cu yd of thatch. 3 cubic yards to pick up and haul away if using a sod cutter, and easy to pick up. If using a powerrake (with FIXED blades), you will break up thatch into little pieces, need to rake it up, and will fluff it up so you will get roughly twice the volume.

    I just charge my hourly rate for the powerrake, and then hourly for the cleanup labor, and time and materials on the seed or sod repair.

    You'll be there for days if using only a rake, and you'll really work hard pulling it loose. Need to remove all thatch down to soil in order to have successful repair.

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