Tuesday, July 28, 2020

Here come the C4s! Warm season grasses start flowering

Schizachyrium scoparium - Little Bluestem
Spikelets of Schizachyrium scoparium
I noticed that two of the grasses I care for at home have started to flower, and both are warm season grasses.

A warm season grass of course refers to a species which reaches its optimal growing rate when the season temperatures are high, normally during mid-Summer. Cold season grasses on the other hand tend to grow fast and flower earlier in the season.

Interestingly enough, the difference between these two groups lies in the way they photosynthesize.

Warm season grasses have C4 photosynthesis, wherein the first carbon compound produced during the process has 4 carbons, whereas cool season grasses have C3 photosynthesis, in which a 3-carbon compound is the initial product.

C4 grasses are much more productive in photosynthesis during hot and dry conditions. So just when C3 cool season grasses start to slow down because of the heat of summer, C4 grasses start revving up their engines.

Schizachyrium scoparium - Little Bluestem
Flowering spike of Schizachyrium scoparium
Two warm season grasses I have are Panicum virgatum 'Northwind', which I purchased a couple months back, and a specimen of  Schizachyrium scoparium (Little Bluestem), which is native to this area, and which I had obtained last year.

I've always liked S. scoparium, ever since I saw fields of this species on a trip to New Hampshire, and its inflorescence is quite distinctive and beautiful to my eyes.

Panicum virgatum 'Northwind'
Spikelets of Panicum virgatum 'Northwind';
The P. virgatum cultivar has also become a favorite of mine, with its erect and tight form and blue green leaves. Its spikelets are quite tiny, and when I photographed them a few days back, they had yet to mature. But I am already looking forward with anticipation to the full panicles maturing, their branches opening up like some botanical umbrella.

Go, go C4s! ;-)

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