Temperature and light have a major influence on how ultradwarf bermudagrass will grow. I've shown the distribution of DLI at Tokyo and Watkinsville, and the DLI and temperature at Fukuoka, Tokyo, and Watkinsville.
Before going any further with calculations and combinations of light and temperature from transition zone locations, I thought it might be illustrative to show how these charts look for a couple non-transition zone locations -- Fairbanks, Alaska, and Hilo, Hawaii.
First, the temperatures. I've included Tokyo as a reference. Remember, Tokyo had an annual temperature, as represented by the cumulative sum of daily mean temperature in 2014, slightly more than Watkinsville, and slightly less than Fukuoka. All those cities, however, were pretty similar. Not so with Fairbanks and Hilo.
Hilo has a tropical rainforest climate, and because the daily mean temperature is almost the same throughout the year, adding them together produces a straight line. Tokyo is the same as what was shown previously. And Fairbanks, where we won't be growing ultradwarf bermudagrass, has a cumulative daily mean temperature in 2014 that just barely stays above 0. The point of showing Hilo and Fairbanks is to point out what these charts would look like in a tropical situation, and in a subarctic one.
As an aside, one sometimes hears of ultradwarf bermudagrass being a big thatch producer, and requiring a lot of work for organic matter management. I would look at it differently, noting that any grass is going to grow at a different rate based first on the temperature and PAR at a location, and secondly based on the nitrogen and water supplied. Clearly, based on temperature alone, an ultradwarf bermudagrass would require no organic matter management in Fairbanks, because there would be no thatch production.
So Hilo is looking pretty good for ultradwarf bermudagrass, by temperature, and how does it look for light? Hilo is 19.7°N, Tokyo is 35.7°N, and Fairbanks is 64.8°N.
Interesting. Fairbanks looks about like I would expect. That far north the DLI in winter is negligible. But how is it that Hilo just barely tops Tokyo for cumulative DLI? That's the effect of clouds, and it is why bermudagrass grows so poorly in Hilo. In fact, Watkinsville in 2014 had cumulative DLI of almost 12,000 -- more than the cumulative DLI in tropical Hilo.
I've mentioned previously the importance of light (DLI) when temperatures are close to an optimum for warm-season grass growth. The climate.asianturfgrass.com website has lots of charts and videos about that.
In these recent posts, I've shown the temperature and the DLI separately. Coming up, I'll add one more transition zone location, and then see what happens when various combinations of DLI and temperature are made.