Hot temps and the effects on grass

Discussion in 'Lawn Mowing' started by eggy, Jun 30, 2002.

  1. eggy

    eggy LawnSite Senior Member
    Posts: 953

    We are seeing very warm temps this year here. It has been in the 90s for some time and more of the same forcasted. We have been recieving rain however it does not appear to be helping with the hot sun beating on the lawns. I have been skipping some, however a lot need to be cut, my fear is that after cuttting the grass from 3.50 to 3.00 it will dry out much faster, what does the hot temps due to the grass? What is the best way to handle hot temps and keep lawns green?
     
  2. awm

    awm LawnSite Gold Member
    Posts: 3,354

    hey eggy. for me a lot depends on how dry it is. if its dry i just trim he tops .
    no matter how high it is. unless im trying to use the mower as a weed killer.:)
     
  3. agrostis palustris

    agrostis palustris Banned
    Posts: 117

    This is something I know a little bit about. By putting it shortly; you are in an area where I am guessing you have C3 turfgrasses? C3 Turfgrasses function well between 60 and 75 degrees F as far as PSN goes. The enzyme that they use to put everything together is called RUBP Carboxlyase. RUBP carboxylase has a slot that is normally used for CO2. However when temps get in the 90's or so... instead of CO2 being put into the RUBP carboxlylase straight O2 goes in there. This is because the O2 is in much higher concentrations than it normally would be in. When the O2 gets into the enzyme, PSN becomes very inneficient. Now don't forget that Respiration (where the plant burns up food) functions better between 85 and 95 degrees or so. So now you are burning up your carbs really fast and you are not making them as fast as you should be.
    Now C4 turgrasses on the other hand.. .the enzyme that they use is called PEP carboxlyase. PEP carboxlyase does not have the slot where O2 can get in instead of CO2.
    Don't forget that C4 turfgrasses also do C3 PSN. Also, in C4 turfgrasses O2 is WAY outnumbered by CO2.
    C4 turfgrasses perform better at temps between 80 and 95 degrees or somewhere like that.
    So that is basically how hot temps effect turfgrass... you are burning up carbs faster than they can be made.
     
  4. agrostis palustris

    agrostis palustris Banned
    Posts: 117

    0h yeah, 3 things you can do to help....
    1) liquid iron chelate apps. No growth, but promotes green (clorophyll) which gives more sites for PSN to occur at.
    2) cut higher, you can greatly enhance your carb population if you cut higher.
    3) if you have the money to do this... dump ice on your turf. this will cool it down so that PSN occurs and cuts down on your respiration.
     
  5. corban

    corban LawnSite Member
    from K.C. Mo
    Posts: 49

    That is some of the most impressive wording I've seen on this website. You lost me with some of the big names but, nonetheless, thanks for giving us some good knowledge
     
  6. GroundKprs

    GroundKprs LawnSite Bronze Member
    Posts: 1,969

    If it gets hot enough, long enough, your C3 grasses will just die, because they cannot supply the food needed to keep growing. The reserves from late spring growth will hold you through the heat of July and August, usually. But a short cool season growing period coupled with a long hot summer will cause the loss of some turf in some areas, and even whole lawns that have significant heating (esp south or west facing slopes in our area).

    I would expect damages in our area this year. We had the wettest spring on record - excess rainfall stressed the turf during the prime growing season. Then the temps suddenly jumped from the 60s to the 80s-90s. If the heat continues unabated to Labor Day, most of my front lawn will die - it's sloped into the sun, and won't be able to survive. The good news: I'll be able to plant newer varieties of turf; will have better color and hardiness than the existing lawn.

    Also, C3 grasses cannot survive when temps get to 113. And remember that temp of turf canopy can be 10-15 degrees warmer than the ambient air temps in early to mid afternoon. Will soon go to syringing my lawns where I control irrigation. Syringing = light application of water around 1 or 2 pm - times can vary in other areas. The water is not to water the grass, but to cool the turf canopy by evaporation of the water applied.

    And that's a cool, concise description, Mr. Bentgrass. Wish I could be so short and specific. LOL
     
  7. awm

    awm LawnSite Gold Member
    Posts: 3,354

    a point of note ,for those in fescue areas. look at the 20-40 yr old lawns
    that have been thru a lot o dry spells .
    those lawns in my area just look like they put it in granny gear ,so to speak,
    and just keep on doin fine.
     

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