To dethatch or not to dethatch

Discussion in 'Turf Renovation' started by integrityman, Sep 22, 2008.

  1. integrityman

    integrityman LawnSite Bronze Member
    Messages: 1,713

    In the next couple of days I will be doing some overseeding on a couple of properties. One of them has a fairly thick layer of thatch buildup from last summers severe drought in N.W Ohio. Normally I am content to simply do a core aeration followed by an overseeding treatment. I try to avoid dethatching as it seems to really tear the lawn up.... it seemds like more and more literature suggests avoiding dethatching. I see things such as: "aerating will allow for air and water to penetrate the thatch which will break it down...." and "dethatching may do ore harm than good..."

    My bottom line is that I want a top notch looking lawn come next spring...

    Any thoughts?
  2. integrityman

    integrityman LawnSite Bronze Member
    Messages: 1,713

    Bump.... thoughts anyone?
  3. joshua

    joshua LawnSite Bronze Member
    Messages: 1,226

    check mail
  4. Whitey4

    Whitey4 LawnSite Silver Member
    Messages: 2,448

    If you are going to aerate, make two passes, over seed and aerate again.

    If you decide the thatch is just too thick, after doing some experimenting on heavilly thatched lawns, my preferred approach is aerate, dethatch ( I do this with with a power rake with a delta reel, designed for slit seeding) remove debris, seed with a spreader, and aerate again.

    The Delta reel will tear up the dying crabgrass in a serious way, and rip through thatch. It will also completely tear up damaged turf, like turf that has serious grub damage. I tried using a seed box whith the delta reel, but it just looked too nasty and the seed distribution was awful. The Delta reel as opposed to spring tines makes a wider slit through thatch, and I believe resuts in better soil to seed contact.

    In those areas where the turf just disappeared after one pass (weak, damaged turf with no root system to speak of) I also spot seed and top dress with top soil.

    So.... I aerate, mow low, use a power rake with delta reel, remove debris, mow again, broadcast seed, and irrigate.
  5. turfcobob

    turfcobob LawnSite Senior Member
    Messages: 878

    Whitey, has a good program. One thing I might add is to check the thatch layer in multiple locations in the lawn. If the thatch is more than .500 to .750 of and inch thick you have problems and that thatch needs to be removed to seed into thatch that thick you are just asking for problems. Get it down to somewhere under a half inch better under a quarter inch.
  6. Whitey4

    Whitey4 LawnSite Silver Member
    Messages: 2,448

    TB... I agree.... if the thatch is thick, you have to set the blades deep, but I've found that doing this will almost completely strip the groud of vegitation on heavilly thatched turf. It becomes darn near a bare dirt renovation. Rip it up enough for a good soil to seed contact, and it means practically sod cutting the old turf right off the dirt.

    I think you know I have a Husky SD22, the bluebird unit. Seriously questionong that buy now... the seed box likes to dump a 1/4 lb of seed when you make a 180 and restart. I don't even use the seed box now... just the delta reels which will remove thatch more deeply and with wider slits than the spring tines will, and then I broadcast seed, but that's about all the "good" things I have to say about it.

    I'd like to try a Turfco... got anyone on Long Island that would'nt mind me checking their Turfco out? I just can't plan to spend that sort on money unless I can get my hands on one first.
  7. Smallaxe

    Smallaxe LawnSite Fanatic
    Messages: 10,082

    Thatch is caused by drought?
    Plz take a moment to read this. Then spend the day thinking about it. Then another moment to investigate the lawns - to see what you are dealing with - b4 running off with a "one size fits all" fix.
  8. Whitey4

    Whitey4 LawnSite Silver Member
    Messages: 2,448

    You lost me here... who said thatch is caused by drought? And what "one size fits all" fix are you talking about?

    As I see it, this is a thread about ONE way to deal with thatch... no one said it was the only way. Sure, thatch is caused by an accumulation of conditions. I think I know where this is headed... yes, too much fert, N specifically contributes greatly to thatch build up... but we are talking about how to start to fix the problem, and what approach is best.

    I saw nothing in that article (not a bad one at that) that contradicts what has been discussed here. Care to elaborate on your sort of directionless comments?
  9. Smallaxe

    Smallaxe LawnSite Fanatic
    Messages: 10,082

    My point was that, if we are looking at thatch reduction we should be talking about thatch and not a mulch build up of dead grass leaves.

    There is a big difference and we should be addressing an actual problem not something that we do for the money every autumn. Hence the 'one size fits all', remark.

    If you are talking about the article I posted then -what needs to be observed is the definition of thatch. [purpose of the article] Thatch is thatch and drought is not going to accumulate excessive thatch quickly in one summer. In fact drought is not going to accumulate thatch at all.

    If my point was lost in the posting perhaps I could reiterate about what thatch is , because I am interestted in knowing whether integrityman has a thatch problem b4 I start saying what he can do to fix it. It sounds to me like he has a bunch of dead grass blades because of a drought.
  10. Whitey4

    Whitey4 LawnSite Silver Member
    Messages: 2,448

    OK, I got ya. While a mat of dead grass is not thatch by definition, if seed cannot penetrate the dead debris and get to soil, it still has to be broken up, or "dethatched" to misuse the word in the technical sense of the definition.

    For example, severe grub damage also results in a "mat" of dead grass. It isn't thatch, but must be mechanically removed somehow before attempting to over seed the area.

    I think it's good discussion to bring up thatch and it's causes, and to differntiate thatch from dead matted material which is very different, but both require removal before reseeding can be done. For matting in small areas, patch repairs, I prefer the old iron rake to get surface dead material removed. If it's a large area, I would use a machine for removal. The difference is in how deep I would set a delta blade for matted vs. thatch conditions. Having said that, I often find that thatch was a cause of grass to fail and mat down.

    Like Turfco Bob said, thatch, or more accurately turf, should be inspected at several locations to inspect how deep the thatch layer actually is. Even if a grub damaged stand of dead matted grass may lift easilly because it has no root system left, there may or may not be a deep thatch problem. That is the first step in diagnosing a treatment approach... know what one is dealing with. With some investigation, how to treat, and if needed, how deeply to dethatch becomes obvious.

    I think we're on the same page, but you first post had me scratching my head a bit without references to the comments you directed your post towards.

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