The other day I idly noticed this leaf on the ground.
Hmm, big leaf, I thought. It was from a young breadfruit tree (Artocarpus sp.) – I knew that. I simply hadn’t thought of breadfruit leaves as big before. There they are up in the tree. Once I looked, I realized that they are big.
Banana (Musa sp.).
Bijao, or Calathea lutea, in the same order, Zingerbales, as the banana.
Resurrection plant (Curcuma sp.), also in the same order as banana.
(Okay, I cheated on the last three images. They’re old ones from my iPhoto library, and the Curcuma is just now flowering, the leaves are not up yet. Everything else, though, really was photographed yesterday.)
“Elephant ear” (unidentified species).
Teak (Tectona sp.)
So, I started asking myself a question, the answer to which is really obvious to anyone who has studied ecology, but I needed to re-think it.
What I learned in ecology, and what I see for my own eyes every time I look for it, is that leaves of plants that grow in the shade tend to be bigger than the leaves of plants that grow in the full sun. The usual explanation is that a large surface area is needed to gather sufficient sunlight for photosynthesis when the intensity of sunlight is low.
But I’m looking at these bananas growing in full sun. Likewise the Cecropia, which is a canopy tree, growing above all the other trees in my back yard “woods.” Likewise the breadfruit tree, the Calathea, the Curcuma. The only leaf that matches my idea of growing in the shade is the elephant ear. Possibly the teak, which is growing up in the woods, but there’s a teak farm not far from here and it’s out in the full sun. The trees are not shading each other at all, since the trees are tall and skinny.
So what’s the story?
These big-leafed plants are growing side-by-side with, or even above, average- or small-leafed plants.
I did a little scrounging around on the internet looking for an explanation, but all I found were statements like, “Big leaves are well suited to rainy climates, so many trees that grow well in rainy places have them.” With the added observation that in climates where there is a lot of rain, there is less sunlight than in climates where there is not much rain.
Well, okay. We do have a lot of rain in the rainy season (especially last year), but here in the savanna the forest is a “dry” forest, not a “rain” forest, so in that respect, I don’t think of here as a climate where there is a lot of rain.
One thing I have to remember, though, is that some of these plants are not really native to this area. Bananas, breadfruit, Curcuma, teak, no. The elephant ear, yes, and it is growing in the shade. I could assume that these non-native plants would rather be living in a rainier, more moist, and therefore more overcast, environment. So all these large leaves may be more useful in their native environment than they are here in this savanna, where we have at least two months of the year of very little or no rain.
That leaves Cecropia as the only real puzzle. Maybe it’s not such a puzzle, now that I think of it. Cecropia trees have very few leaves, and the ones they have drop off frequently. I’d bet that if I measured the entire surface area of the leaves of a Cecropia tree and compared it to the surface area of the leaves of its neighboring, but lower, trees, that the Cecropia would have a smaller total surface area than the trees below it.
Just some idle thoughts.