Back in May, I noted the early blooming of Miconia rubiginosa after the heavy rains in April.

Now, in July, I’ve seen two plants in bloom that I normally see bloom in August: a tree with large bunches of yellow flowers, Senna hayesiana, and a miniature relative of the Elephant Ear herb, Xanthosoma mexicanum. I’m also seeing flower buds on an unidentified Miconia that usually blooms in September. I’m sure more’s going on along this line than I’m seeing.

Maybe these large swings in time of blooming are relatively normal for the tropics. But I’m starting to think that it’s more than coincidence that different plants from three unrelated families (Senna = Fabaceae or bean family, Xanthosoma = Araceae or arum family, Miconia = Melastomataceae or “black mouth” family)  are blooming immediately after uncommonly large monthly rainfalls.

The morning sunlight shone through the hood, making a glow like candle-light.

Hoping it might be easy to identify, I ran to my borrowed copy of the Flora of Panama Checklist and Index and looked up Arum – the jack-in-the-pulpit genus – and found four species. It did not take long to discover that this plant was none of the four species listed. So, being impatient and eager to get on with the ID, I turned to friend Carla, who did a little research and then turned to her friend Marianne, and behold we had a name – Xanthosoma mexicanum, previously known as Xanthosoma pilosa.

Sometimes (maybe I should say often) plant identification is just a matter of knowing who to turn to for help!

Edible and poisonous

The Xanthosoma genus is in the same family as the Arum, the Araceae Family. The family takes its name, in fact, from the Arum, a word that may have been derived from the Arabic word for fire, ar [Britannica]. That’s because the sap of and Arum plant and others in this family have a bitter, burning taste due to calcium-oxalate crystals and other toxins [Zuchowski]. These toxins can

…cause swelling and burning of the mouth and throat if eaten raw, as well as diarrhea and vomiting. The juice of the plants may irritate skin and eyes. [Zuchowski]

Cooking, however, can make the plant edible, and the tubers of some of them are used for food. Taro, called ñampi here in Panama, is in the Araceae family, and is used in several dishes of Panamanian cuisine.

Elephant ears

The best known Xanthosoma among gardeners in temperate climates is probably Xanthosoma roseum, the elephant ear. Those leaves may reach 200 cm in length. (Photo from wikipedia.)

Our little Xanthosoma from the orchard, Xanthosoma mexicanum, though, has leaves about 6 cm long. Please excuse its I-survived-the-weedeater appearance!

The yellow body
The word Xanthosoma was coined from xantho, meaning yellow, and soma, meaning body. I’m assuming the yellow body referred to is that part – the spadix – sticking up under the white hood – the spathe. And here we come to the whole reason for putting together this post.

Those two parts – the spadix and the spathe, defined below – are characteristic features of the Araceae family. They are the features of the calla lily, the jack-in-the-pulpit, and skunk cabbage that make the family so interesting to look at. I’ve been curious about these features for ages but only now have had the motivation to learn more about them.

The spadix continues down beneath the red throat of this little plant into the green belly below. I didn’t want to tear apart my one flower just to see what’s inside, so I borrowed an image from Discover Life, where the copyright allows use for personal and scientific reasons. Go there for the high resolution version of this image. The image below combines three views of the spadix and spathe – at the top is the complete structure, in the center is an enlarged view of the top portion of the spadix, and at the bottom is the portion of the spadix that is hidden in my plant.

The spadix and the spathe
A spadix is a cluster of tiny flowers crowded together on a thick, fleshy axis; the spathe is a modified leaf called a bract that either lies just below or partially encloses the spadix (wikipedia).

If we look closely at that upper section of the spadix, the section that’s a little reminiscent of immature corn on the cob, we see the male flowers of the plant. The tiny tufts sticking out between the hexagonal shapes are the anthers bearing the pollen grains.

The bottom portion of the spadix has the female flowers (the bright yellow “corn kernels”) on the left and a belt of sterile flowers (yellow, white, and purple) offered as a reward for pollinators on the right. The pollination story that follows is taken from the wikipedia article on Xanthosoma. It’s a neat tale.

When the top portion of the spathe first opens and exposes the spadix, it produces heat and releases a sweet scent that attracts its pollinators, which are scarab beetles of the Cyclocephala genus (drawing used by permission of Joe McGown).

These beetles presumably arrive covered with pollen from another Xanthosoma inflorescence and they remain in the spathe tube for 24 hours, pollinating the female flowers as they feed on the sterile area of the spadix.

On the second night, they come out of the tube and walk over the male flowers, getting covered by pollen, and then they fly on to another recently opened Xanthosoma.

Fruits start to develop while still sheltered by the spathe tube, and maturation takes months. When the fruits are mature, the spathe tube rolls open to reveal bright orange fruits and a velvety pink inner spathe surface.

Wow! I have no idea whether my single, isolated Xanthosoma mexicanum had a chance to be fertilized, but I’ll try to keep the weedeater away long enough to find out. Meantime, I have seen some other leaves of the plant on the ground nearby and I may try transplanting some to a safer area.