Senna hayesiana

In my last post, I wrote of finding a tree with yellow flowers growing along a seasonal stream here at the edge of our property. The flower looked a little like the flower from the Scrambled Eggs tree (Cassia surattensis), as described in the books I have available. Unfortunately, the images I found on the web of flower itself looked somewhat different from the flower I had in my hand.

I’ve now learned, with a lot of help from a good friend and from a graduate student in Switzerland, that the tree is most likely Senna hayesiana.

I learned a great deal about botany in general and about Senna (a genus formerly known as Cassia) in the process.

By the way, when I find the scientific name of a plant I’m interested in, I always check Dave’s Garden Botanary for the root meaning of the words.

Senna is the “Latin form of Arabic word for a thorny bush,” and hayesiana is “Named for Sutton Hayes, 19th century doctor and naturalist with the El Paso and Fort Yuma Wagon Road Expedition.” The tree I’ve sampled is not thorny, interestingly enough. The earlier name Cassia is “From an ancient Greek name Kasia used by Dioscorides.” [My problem is that then I had to look up Dioscorides in Wikipedia only to find that he wrote "...one of the most influential herbal books in history," Materia Medica.]

While searching for Senna and Cassia links on the internet, I found a very interesting poster, available as pdf, on the evolution of asymmetric flowers in Senna. I thought I saw an image on that poster that looked very similar to the flower I had in hand. I wrote to Brigitte Marazzi, the senior author, who is studying at the Institute of Systematic Botany, University of Zurich, and she responded promptly to my email query. She nicely confirmed my impression and pointed me to her interesting website.

Cecile Lumer, a friend and botanist in Arizona who has worked in the tropics, put up with my incessant and naive questions about this flower until its name was finally pinned down.

I’ve learned that flowers can have sterile reproductive parts, that there can be glands containing nectar on parts of the plant other than the flower, and that certain parts of a flower may fall off even before it blooms! One thing I haven’t learned is why the genus name Cassia was changed to Senna.

The quest continues.