Mandevilla hirsuta – plebian trumpet vine

This flower almost always catches my eye as a lone spot of color in a tangled field of grasses and shrubs.

When I get up close to it, I feel an odd deja vu. Only after identifying it, and finding its family and its elegant relative, did I come to understand why.

I figured this plant was not going to be all that easy for me to identify. It was and it wasn’t. I thought I had it figured out as Odontadenia macrantha, but luckily, Robin Foster of the Field Museum of Chicago caught my error. It turned out to be, probably, Mandevilla hirsuta. More on that in a bit.

Most of my books are devoted to trees and shrubs, not vines. The flower did remind me of periwinkles and the common (in Central America, anyway) allamanda or golden trumpet vine. Those flowers are in the Apocynaceae, or dogbane, family. However, my identification skills are still so naive that I thought it best not to assume the family name right away.

I turned to an online key, Discover Life Flora of the Neotropics which has a database of 8,246 kinds of plants. It’s designed for novices like me and takes one through a series of multiple-choice steps, which include region where the plant was found, altitude, habit (tree, shrub, vine, etc.), leaf arrangement, leaf shape, flower color, and a little more.

My leaves are simple, opposite, with smooth edges.

Also important, I thought, was the fact that when I pulled a leaf away from the vine, I saw a copious amount of milky sap, or latex.

So, with the characteristics I entered, I got 37 matches. The results were listed on the left hand side and were organized by genus and species names, so I did not know what families the various plants were in. The only thing for it was to look at images of each of the 37 plants until I found one that fit. My consolation was that 37 plants were a lot fewer than eight thousand!

I was about halfway through the list when I found a page from the Smithsonian Tropical Research Institute filled with copyrighted images that gave a satisfying match to my plant. It was identified as Odontadenia macrantha, a member of the Apocynaceae family.

Okay. As you know by now, I misled myself by those photographs, but at least I was in the right family.

So, to check the characteristics of the Apocynaceae, which have about 200 genera and about 2,000 species, which are particularly obvious in this plant. From wikipedia:

1. Leaves simple, usually opposite. Check.
2. Flowers usually showy and radially symmetrical. Check.
3. Stamens inserted inside the corolla tube. Check.
4. (from several other sources) Milky latex. Check

Fine. A member of the Apocynaceae, or dogbane, family. The roots of this family name, by the way, are, according to Dave’s botanary, Greek: apo, meaning away from or away with; kuon, meaning dog. The dogbane plant, an Apocynum species, is reputed to be poisonous to dogs.

This information on the toxicity of plants in Apocynaceae comes from kingsnake:

Many of these plants possess deadly toxins. However, they are notorious for being the larval food plant of a number of insects. Particularly, some sphynxid moths’ caterpillars incorporate the plants’ alkaloids to their own tissues, thus becoming toxic themselves. Several species of Plumeria are found in the Caribbean. They usually have large, colorful flowers with a sweet fragrance.

Many plants, however, produce toxins that are poisonous in high concentrations but may have medicinal benefits in lower doses. As the Encyclopedia Britannica points out:

Arrow poisons are obtained from many plants in the dogbane family, and the poisonous alkaloids of species belonging to the genera Strophanthus and Rauwolfia (qq.v.) also are used in medicines.

Indeed, a toxin from Odontadenia macrantha has been shown to be moderately toxic against A2780, the ovarian cancer cell line, according to an article published in Magnetic Resonance in Chemistry in 2003.

As to that error in identification, Dr. Foster explained to me that the Discover Life site just doesn’t have enough images to identify every specimen. The Mandevilla could have been among the 37 on my list, but it would not have had a picture to show what it looks like. If I’d had more patience, and stayed with that list of 37 until I had a picture (from elsewhere on the web) of every species on it, I would, I hope, have chosen the right species. Now I know I should have gone straight to Tropical Plant Guides and searched for the genus names there. Had I done so, I would have found this great image of Mandevilla hirsuta.

Dave’s Garden says that Mandevilla was named for Henry Mandeville,18th century British diplomat in Argentina; hirsuta means hairy, and, yes, the leaves are hairy.

Now, back to that sense of deja vu whenever I see the Mandevilla. Look again at the petals, their skewed shape and their flat and ruffled edges. I find that shape very appealing, and in reading up on Apocynaceae, I saw why it looked familiar. It reminds me, though faintly, of the frangipani, or Plumeria. The frangipani petals are also skewed and have essentially flat edges. They are more separate from each other, though, than are the petals of the Mandevilla and overall they have a much more elegant and sophisticated look. (This image is from a web site on St. John, US Virgin Islands).

Nevertheless, even if my deja vu was off base, I’m satisfied to think of the Mandevilla as a plebeian relative to the regal Plumeria.