In this chart, I plotted the mean daily light integral (DLI) on days when the mean temperature is ≥ 24°C (75 °F) against the accumulated warm-season (C4) growth potential on those same days. That is, I selected only the days of the year when it is relatively warm, and then estimated the average amount of photosynthetically active radiation that will fall on the ground on those days.
Why am I writing about this today? Because I think this chart can be used to help explain something that I've received a couple inquiries about. And that is the locations at which I suggest manilagrass (Zoysia matrella) would perform better than bermudagrass (Cynodon spp.). I only recommend manilagrass as the preferred species when the light is low.
Take Dubai and Florida, for example – and these were the locations I was asked about. The light there is relatively high, and I would suggest the default species be bermudagrass, rather than manilagrass, unless there were contributing factors such as tree shade that would appreciably reduce the light.
I've written about manilagrass as the fine fescue of the tropics, and by that I mean places that have a tropical climate. All the cities at bottom right of the chart have a tropical climate, and some of the cities on the left side of the chart have a tropical climate. What is particularly distinctive about most places with a tropical climate is the lower amount of light available for photosynthesis during the time of the year when temperatures are warm, compared to the amount of light in locations with a different climate.
In locations on this chart with mean DLI less than 42.5, I expect there to be some challenges with growing bermudagrass as a closely-mown turf, due to the lack of photosynthetically active radiation. In most of those places, manilagrass will outperform bermudagrass.
In locations on this chart with mean DLI more than 42.5, I expect bermudagrass to outperform manilagrass, due to the relatively high amount of photosynthetically active radiation.