Senna hayesiana in bloom
Yesterday Steven Alexander of Tropical Biodiversity published a beautiful image of a Senna tree in flower. It was incentive enough for me to go look at our own Senna, Senna hayesiana, which has been in bloom since August.
The pre-dawn light and my camera settings make the flowers look a brighter yellow than they are. Imagine a paler shade. If you have Steven’s image up for comparison, the color of the Panama flowers are somewhere between the two images.
This particular Senna is among the few trees in our area that are in bloom this time of year, and because they tend to grow at the edge of woods, their color really stands out against the various shades of green.
Or, for that matter, against the brown of a rock wall or the blurry brown of a Lab in motion.
The flowers are pollinated by insects. There’s a Senna hayesiana behind our bodega, near our compost bins. If the tree is in bloom when I empty the compost into the bin, I inevitably hear the buzzzzzz of bees. This morning I saw a bumblebee nearly half as large as the flower itself, but of course, I had a compost container in my hand rather than my camera.
I do have a picture from three years ago of a bee at work on the flower, but I’m putting it after the break because the color of the flower is so jarringly different from the colors in today’s images. (Camera differences, ambient light conditions, among other variables – I’m not knowledgeable enough with photo editing software to make color corrections.)
You’ll see the bee poised at the end of the green, curved pistil, the female reproductive structure.
That pistil is going to elongate to form the fruit, which is a bean. In the image below, you can see the beans and also the pistils that were left behind after the petals dropped. It takes a couple of months for fertilized pistils to grow to full size – this picture was taken in October after a bloom that occurred in August.
As a member of the bean family, Senna has compound leaves, arranged alternately along the stem. Each leaf (bracketed) is divided into four leaflets. Most of the leaflets in this image were about 10 cm long.
Panama has several species of Senna and many, including even this one, are used as ornamentals. But in August and September, at least here in Chiriqui, the only Senna that brightens the normally gloomy rainy season is this one.
More information on Senna hayesiana is given in earlier posts, starting here for ID and here for biology.
PS: Very belatedly, I’d like to draw your attention to the plant carnival, Berry Go Round. Edition #19, at Quiche Moraine, is a light-hearted but rigorous look at blog posts on plants that appeared toward the end of summer. If you haven’t already, go look, and enjoy yourself!
Great post on Senna hayesiana. I grow Senna alata for the benefit of Sulphur butterflies and the stunning blossoms at this time of year.
My grandchildren lived for 18 months in Panama when they were much younger. They were able to tell me a little about the flora there. I enjoy growing the tropicals that survive our mild winters here.
Like many arborescent fabaceous genera, Senna is a favored host for jewel beetles (family Buprestidae) – we have discovered several new species on different members of this genus in Mexico and assume that the beetles develop as larvae by boring in dead branches of the host.
Welcome back!
regards–ted
Hello Nell, and thanks for commenting. Senna alata is more spectacular than S. hayesiana, so I can see why you would choose to grow it. Interesting that it’s in bloom this time of year in your neck of the woods.
Ted – Thanks for the tip. I’ll start watching for jewel beetles and paying attention to the dead branches. I hesitate to mention it, but I have seen a cockroach land on a S. hayesiana flower. Can I hope that was just a coincidence? The habitat is a “tangled bank” near a seasonal stream, fine habitat for cockroaches, and snakes, as well as Senna and other wonderful trees.
Thanks for the welcome back – my re-entry’s a little bumpy but I hope to get up to speed in a bit.
Hi! Great to find this blog! I am the person you contacted a few years ago in Zurich (Switzerland) to confirm your identification of Senna hayesiana
I am glad you are observing this species so close! You should write a scientific paper on it! This is the only Senna species (out of 300-350) which has only four fertile anthers. I have been studying Senna since you contacted me, and I will be glad to send you pdfs of the articles, if you can’t find them online. The artcile of 2008 on floral symmetries in Senna has a foto of Senna hayesian, probably the one you saw on the poster.
All the best!
Hello Brigette,
How kind of you to comment! Thank you very much for your offer of articles on Senna, which I definitely accept. S. hayesiana is indeed one of my favorite trees, and I’ll be keeping a close watch on it, knowing now just how unique it is. Thank you.