Dissecting Cecropia

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I’d like to introduce you to a very distinctive tree, straight out of Dr. Seuss. In the Puerto Rican rainforest here, you will often see Cecropia schreberiana (Urticaceae) with its long spindly branches and ringed white trunk spiraling up to the highest points of the canopy. It reminds me of a long metal hose with frayed ends, and looks like no other plant you see here. Its spindly form reflects its pioneer strategy. This species grows best in disturbed areas where its ability to deploy leaves on narrow branches lets it grow rapidly and reproduce before being eventually out-competed by slower but more mechanically robust plants. In this way, Cecropias dance between patches of disturbed forest, alighting in each forest patch for just a few decades.

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The species has some strange adaptations that make this lifestyle possible. First, it grows very large leaves with a very distinctive shape. Above you can see an example branch that we cut from 11 meters height in the canopy (the lowest branch we could find, and hard work too). These leaves are able to capture sunlight well in the high canopy without shading each other, thanks to their long petioles. The leaves don’t last forever, though – a common sound in the forest is a crashing, falling noise, as one of these giants hits the forest floor. It sounds at least as loud as a squirrel falling out of a tree.

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On the subject of falling, another adaptation is weak wood. Having only a few leaves at the very top of the tree means that its wood doesn’t need to support much weight, or require much investment. of course this means that even small disturbances can greatly damage the plant. Here you can see a very large branch that fell on our field station after an overnight rainstorm. I woke up one morning and was very surprised to see the path into the kitchen completely blocked by this pile!

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This wood is built in a very curious way. Rather than growing radially and leaving a solid heartwood, like most trees, Cecropia grows these jointed woody segments that are hollow. Hollow wood preserves much of the strength of solid wood (think of scaffolding made from steel tubing) without much of the cost. Above you can see a branch I cut in half.

In that photo, you can also see some strange curved structures. These are male flowers – Cecropia individuals are either male or female, and the male plants disperse their pollen through the wind (which is plentiful in the highest reaches of the canopy). The dangling open structure of these flowers helps the wind catch the pollen.

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And finally, one thought on daily life for this species. In the canopy, there are many risks – bright sun can damage young leaves, and insects can easily chew holes through valuable tissue. Cecropia leaves develop in a protective sheath, after which the young leaf is allowed to unfurl. It’s a beautiful and highly functional structure.

This species commonly reaches heights exceeding thirty meters, so it’s rare to get a glimpse at its flowers and leaves. You may imagine that directly climbing a tree like this would be an unadvisable adventure! As we work our way through this forest, we have certainly found that this is the most difficult species to work with, but also the strangest and most fun. Imagine Cecropia the next time you read Dr. Seuss!

12 Comments Add yours

  1. monomiao says:

    The stem looks like bamboo. How is the smell? In the tropical area in southeast Asia, people use the bamboo to cook rice or soup. Are these plants used for that? Just curious 🙂

    1. bblonder says:

      It is very reminiscent of bamboo, but there are a lot of species that make these jointed stems. For example, Piperaceae, a common tropical family, also do it, though they are very evolutionarily distant from bamboo (Poaceae) or the Urticaceae, where Cecropia is from. I’ve never heard of anyone using them for food, but the wood is decent for flute-making and small carpentry projects. Bamboo I also enjoy in soup and think it has very little competition from this genus!

      1. monomiao says:

        haha, maybe a little misunderstanding? Using bamboo to cook rice or soup, I mean, using bamboo as a container, not part of the food, like in this picture: http://file21.mafengwo.net/M00/14/5B/wKgB3FDpE3aAPHFuAAGsSp_jzyI01.jpeg They are very delicious and smell good because of the bamboo scent. 🙂

      2. bblonder says:

        Wow, I’ve never seen that before! It is a wonderful idea. I think the Cecropia stems would be too small for anything besides a snack.

        Ben

  2. Neat, thanks for the dissection pic. You could also weave to halves together for a makeshift mancala board or come up with a more endemic rainforest game.

    1. bblonder says:

      Cool idea! Unfortunately our permits don’t let us take material out for that, but you should come down here and make one!

  3. I have heard Cecropia has some sort hallucinogenic properties, probably in the leaves so not likely that anything will happen if you use it as a cooking pot, but bear that in mind if your nice starts talking to you.

    1. bblonder says:

      Cool! I looked it up, and this book on Mayan ethnobotany (http://www.maya-ethnobotany.org/FLAAR-Reports-Mayan-ethnobotany-Iconography-epigraphy-publications-books-articles-PowerPoint-presentations-course/1_Mayan-ethnobotany-iconography-plants-food-fruits-sacred-flowers-trees-Guatemala_FLAAR-annual-report-2010-2011.pdf) says that the leaves of a congeneric species are commonly smoked as a marijuana substitute. I wonder what the active chemical is? Cecropia schreberiana doesn’t have a strong odor when its leaves are crushed or its stems are cut.

      1. No idea about the active compound or if it actually works. All what I know is very annecdotical and I haven’t check proper studies (oh science you and your fractals of wonder). But it seems that it may be that C. schereberiana has this property too, but not in all individuals: only the ones without ants! A friend as the hypothesis that as a Cecropia you can either have (and feed) your personal ant army or invest in filling your leaves with funny chemicals. It is an interesting system, lots of things to be tested there. Let me know if you find something interesting.

  4. Michele Glenn says:

    Do the leaves on a very young cecropia start out with fewer segments? I have an unknown “baby” tree in our woods that someone said was a garumo but the leaf is just 3 segments….

    1. bblonder says:

      I’m not sure – I don’t have any nearby at the moment, but it seems likely that the lobes divide more finely as the leaf gets older. Keep watching and keep me posted!

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