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Bermuda and frost

Discussion in 'Pesticide & Herbicide Application' started by ThreeWide, Nov 19, 2005.

  1. ThreeWide

    ThreeWide LawnSite Bronze Member
    Posts: 1,116

    One thing in particular I have learned this season about Bermuda:

    When mowed at lower heights (1.5" or less) the turf retains color MUCH longer. I have lawns located on the same street that are maintained at various heights. The higher cut lawns (2" and up) were the first ones to go dormant from the frost.

    The reel cut lawns have retained color as much as 1 month longer for example.

    My theory behind this is that the lower cut turf retains warmth as it is closer to the soil. The higher cut turf is more exposed to the colder air, so it stops photosynthesis much sooner.

    Certain areas also have microclimates that effect dormancy, but this rule seems to hold true.
  2. dwc

    dwc LawnSite Senior Member
    Posts: 626

    I have noticed a lot of different varieties of bermuda go dormant at different times also. Some hybrids will go dormant different than common for example.
  3. ThreeWide

    ThreeWide LawnSite Bronze Member
    Posts: 1,116

    That is also true.

    I should have mentioned in my first statement that the subject was limited to hybrids, 419 and 328.
  4. Az Gardener

    Az Gardener LawnSite Gold Member
    Posts: 3,899

    At about late Aug early Sept start using a fert that is higher in Potassium that helps too. We use a 6-20-20. I think you are right shorter turf means the sunlight is closer to the soil and can keep it warmer longer. All that air space in the taller grass I would think keeps the sunlight /heat away from the soil allowing it to cool sooner.
  5. quiet

    quiet LawnSite Senior Member
    Posts: 720

    I'm not finding the same correlation between cut height and the onset of dormancy. I think the "shading" or "insulating" notion is silly, particularly when given the very small variation in cut heights in bermuda hybrids. Does a lawn cut at 2.25" insulate differently than a lawn cut at 2.00"? I'll grant that turf density is improved at lower cut heights, but how much "insulation" is there?

    I think a somewhat better correlation can be found in localized temps on any given property as we dip near freezing in late fall. Some lawns (and soils) get cooler than others - and for longer periods - as winds die down and air temps dip - even within the same neighborhood. Cold air "pools" in low spots on calm nights.

    I have one lawn that is almost completely dormant that's three houses away from another lawn that's still going strong. The homeowner at the dormant lawn is slightly downhill from the others, and told me he had a light frost on his lawn and roof late last month. Both lawns have been cut at 2.25". Both are Tif 419.

    I also do two properties next door to each other, one is going dormant, one not. Both cut at 2.00". Both 419. Neither waters correctly, and we've had a bad drought and a long hot summer.

    Too many factors to make definitive judgements.
  6. ThreeWide

    ThreeWide LawnSite Bronze Member
    Posts: 1,116

    At the onset of frost, soil temps are normally at least in the 50 degree range or possibly higher. Low cut turf benefits from the warmth of the soil, while higher turf gets cold air exposure.

    This assumes that lawns in comparision have been watered and fertilized adequately.

    Lawns that were not adequately watered went dormant quickly regardless of height.

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