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Cold Tolerance

One big difference between heat stress and cold stress is cold stress can have an impact on warm season turfs AND cool season turfs.  Whereas heat really only affects cool season turfs.  Warm season turfs usually thrive in warm weather.  As logic might dictate, cool season grasses are a little more tolerant of cold temperatures than warm season grasses.  

As I’ve said many times in this blog, you got to select the species that is best adapted for the region you are growing the grass.  That is not only the turfgrass adaptation zones (See my blog post on: “Turfgrass Adaptation”), but it also means the immediate environment…your yard…your playing field.  Is there poor drainage?  Is there lots of shade?  Is there only direct sunlight?  What is the annual or seasonal rainfall?  What is the use of the stand or area – high use or low use?  You have to look at all sorts of issues.  

I will list below the cool season turfgrasses that are most tolerant to the least tolerant of cold stress:  

Rough Bluegrass
Creeping Bentgrass
Kentucky Bluegrass
Annual Bluegrass
Tall Fescue
Perennial Ryegrass
Annual Ryegrass  

The warm season turfgrasses most tolerant to least tolerant of cold are:  

Zoysiagrass
Buffalograss
Bermudagrass
Bahiagrass
Centipedegrass
Carpetgrass
Saint Augustinegrass  

As I mentioned earlier, drainage is important.  Drainage is even more important in the case of cold tolerance.  Okay; it is bad to have your turf submerged for long periods of time.  Now, imagine your turf not only submerged but that water also freezes.  And, it is a nice long, deep freeze.  Not good.  Keeping turf excessively wet or frozen is a primary reason for cold weather kill.  

You need to ensure not only surface drainage but also subsurface drainage.  Both of these considerations are directly linked to the “type” of soil you have.  What percentages of sand, silt and clay do you have?  Sand is porous; clay is not very porous.  What this means is you may have to do some civil engineering on your property.  You may need to change grades, install drains (french drain, perimeter drain, filter drain, collector drain, interceptor drain, fin drain, weeping tile, blind drain, rubble drain, rock drain); that sort of thing.  That usually involves digging, laying of sand or gravel; maybe even some landscape fabric and installing some sort of pipes and/or grates/basins.  This is not an inexpensive endeavor.  And, do us all a favor, if you do this yourself; call Miss Utility before you even think about touching a shovel.   

Judicious use of nitrogen fertilizers also applies here.  I’ve written about getting a soil test to find out your requirements, seasonal or monthly applications, etc.  In the past, my discussions about nitrogen fertilizers have been regarding its affect on the environment.  Well, in this case, excessive late season applications of nitrogen can increase the lusciousness of the turf.  That’s very nice, but it makes your turf more vulnerable to disease.  And, if the turf is too succulent, it will be more susceptible to low temperature stress as well.  

Also, with regard to fertilizer, maintaining adequate phosphorous and potassium levels is important.  Potassium is especially critical to ensure cold weather tolerance.  Some studies have shown that the balance or ratio between NP & K is very important.  Cool season grasses show good cold hardiness if the N to K ratio is about 2:1 or 3:1.  Warm season grasses should be fertilized in late fall with something like a 4-1-6 NPK ratio for good cold weather tolerance.  

Finally, more topics I’ve already laid out for you – mowing high and maintaining a low level of thatch also help with cold weather hardiness.  Mowing high increases photosynthesis capability and helps grow deep roots.  While reducing thatch helps the soil surface dry out better and you won't have that moist layer remaining cold and have that layer freeze.

Next, I will get into shade tolerance.  This also goes back to my earlier topic where I discussed “turf or trees” in my “Heat Tolerance” blog post. 

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