Sunday, March 28, 2021

A meeting of giants

Flowerhead of C, purpureus
I admit I am not your typical tourist. Sometimes I like to wander the streets of cities I visit, just looking at all the flora and fauna to be seen. This was the case when I visited Florida City in Florida, which is close to Everglades National Park and Key Largo.

I was walking along the sidewalk of a busy street in this smallish city (ok, it was Route 1, a state highway!), when I had to do a double take. Along a dead-end side street next to one of the many motels in that area was a long row of gigantic grasses! 

Long row of gigantic grasses
They were tightly packed and stretched in an unending row from the start of the street (SE 1st Ave) to its end near the motel back. The grasses rose to 4 meters in height or more, and above some were whitish flowerheads.

Schoolbus parked next to C. purpureus for scale. 
My first thought was that I stumbled on Arundo donax, but a quick inspection of the flowerhead nailed the species as Cenchrus purpureus (syn. Pennissetum purpureum), which has various common names such as Napier grass, elephant grass, and Uganda grass.

Young C. purpureus spreading across a recently fallow lot
The grass had spread from the row to infest a field of trees behind it. The land looked abandoned, but a quick look at Google Street View from previous years showed that it had once been carefully tended, with palms planted in neat rows. Now young Napier grass sprouted from all over the field, and I was thinking that without tending that the lot would soon be filled with it. I also encountered another large stand of Napier grass east of the motels, along with smaller clusters that must have been derived from the larger stands (see image below).

C. purpureus in yellow, N. reynaudiana in red.
Interestingly enough, I spotted other large grass stands in the distance in the empty lot, but a quick look showed that they were a different species!

I trudged into the lot and found out that the new grasses were Neyraudia reynaudiana (Burmareed), their gigantic forms topped by huge plumes of brownish flowerheads. They were scattered in small clusters, and the nearest group was about 30 meters away from the equally tall Napier grass.

Neyraudia reynaudiana
I wondered what would happen when the two species finally met in that empty lot. Would one species be dominant over the other, or would they coexist, the two groups forming a field of gigantic grasses with distinctly different flowerheads? Which grass would prevail in this clash of giants?

Another interesting thing is that I have seen both species all over Southern Florida, but they both become much rarer as one travels north. I have not seen Burmareed in Lake Okeechobee (though I have seen what I took to be Phragmites australis in the distance next to the lake), while Napier grass was quite abundant on the northern lake shore. However, once one gets closer to Orlando, the glimpses of giant grasses becomes rare to non-existent, and I have only seen one cluster of Napier grass in the Orlando area. The specimens were located in Shingle Creek Regional Park, and they seemed a bit unhealthy looking.

N. reynaudiana on the road to Everglades National Park
It is a change to the landscape that is quite evident, perhaps even to the eyes of laymen. The land of giant grasses transforms into a land filled with Andropogon sp. and Aristida sp., much smaller grass species that nevertheless dominate many areas in a way that even the giants might envy.

Spider lurking in a C. purpureus inflorescence

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