Any appreciable difference in soil temp effects on KBG/TTTF?

[chisey]

I only have experience with TTTF, but I introduced some KBG in my overseed/repairs this fall and am curious if I should expect any difference in root growth over the winter. You may recall from previous posts that 4" soil temps in my area almost never get to freezing, and according to the info below that may mean root growth never completely stops.

Cool Season Grasses
90F Shoot growth ceases.
77F Root growth ceases.
70F Maximum temperature for root growth of any consequence.
70F Time to plant grasses in late summer.
60-75F Optimum temperature for shoot growth.
50-65F Optimum temperature for root growth.
40F Shoot growth ceases.
33F Root growth ceases.
20F Low temperature kill possible if temperature subsequently drops rapidly below 20F

The question I have is whether there's any real difference among the cool season grasses at the low end of the above scale, since there's definitely some difference at the top when it comes to heat tolerance. What I'm hoping is that KBG may grow more at temps in the 30s and 40s than TTTF does, since root growth right now may be critical when summer hits the transition zone next June.

Plus I'm just curious. TTTF, KBG, Ryes, etc. are quite different in some important ways so it would be surprising if they all closely followed the scale above.

[Green]

An interesting question. I'm sure they must vary...an interesting tag-along question: Does Rye grow faster than KBG and have less cold tolerance precisely because it's growth trajectory is skewed to somewhat warmer temps? It seems to have a narrower range it prefers than TTTF or KBG...experiencing winter kill at higher soil temps and dormancy at lower temps...but within a certain range, it grows very fast.

And TTTF germinates better above 70 degrees than below...it's used in the transition zone because of its better heat tolerance than KBG.

What about rhizome count and length in TTTF? Correlation to soil temperature?

I think you're onto something...

[John_in_SC]

The major difference I have noticed is on the opposite end of the spectrum.... The KBG goes dormant far earlier than the TTTF when the soil temps get hotter.... My summer lawn looks pretty raggedy through July and August... but it sure did come back strong by October as the KBG came back out of dormancy....

Now.. On the cold weather end... Well.. My wife was teasing me pretty bad when I was out mowing the grass on February 1st last year.... You will find it depends on your microclimate more than anything...

Thanks

[chisey]

The major difference I have noticed is on the opposite end of the spectrum.... The KBG goes dormant far earlier than the TTTF when the soil temps get hotter.... My summer lawn looks pretty raggedy through July and August... but it sure did come back strong by October as the KBG came back out of dormancy....

Now.. On the cold weather end... Well.. My wife was teasing me pretty bad when I was out mowing the grass on February 1st last year.... You will find it depends on your microclimate more than anything...

Thanks

I am nestled in the TN Valley between the Smoky Mountains and the Cumberland Plateau and live about 2 miles from the Tennessee River. It's exceedingly difficult to put a succinct description on our microclimate. Sometimes the mountains and the plateau seem to form a shelter from the severe weather that tends to plague other parts of TN, and at other times they seem to form a tunnel that can channel tornado-spawning storm systems that wreak havoc on the valley. Sometimes they seem to drive rain north and south around us, leaving us bone dry, and at other times they seem to trap it and unleash downpours. Temperatures are less moderated by the elevation than you might think and the summers can be as brutal as those around Memphis if we're unlucky. There's no SCAN site within a few hundred miles so I have no way of really judging soil temperature and moisture history; I'm only using an educated guess to judge that the soil 4" down almost never freezes here.

Bottom line: the potential for success of KBG in this area is a guessing game. My yard is small enough that the extra water, extra fert, etc. are not going to break the bank if I try to give the KBG its best chance of success. It'll be interesting.

[John_in_SC]

Soil temp is actually pretty darned easy... Use your handy dandy digital kitchen thermometer... They sell for ~12.00 at any big box store... Then - you know the truth in your actual yard... not at some site 100 miles from you...

[GaryCinChicago]

The question I have is whether there's any real difference among the cool season grasses at the low end of the above scale, since there's definitely some difference at the top when it comes to heat tolerance.

The major difference I have noticed is on the opposite end of the spectrum.... The KBG goes dormant far earlier than the TTTF when the soil temps get hotter....

Should be noted to both quotes -

It's all about roots.

TTTF will have deeper roots just by its genetics and root depth effect is witnessed both in winter and summer, and also depending on your locale.

Put it this way. 4" KBG depth temp in SC might be way different than 6" TTTF depth in TN. That said, mowing February 1st is 100% feasible.

And northern Maine - it wouldn't matter. KBG at 4" or TTTF at 6". Summer or winter - both seasons are cold compared to SC and TN.