A Neotropical Savanna

My blog break is nearly over and I’ll be posting another plant identification puzzle this week. Meantime, during the break, a few comments on older posts have come through. One comment on Palo Blanco – White Stick or Pole was so interesting to me I thought it deserved some special attention.

Here it is, from Juan:

I feel so grateful for this piece of information. It [the tree] is highly valuable for the honey industry in Panamá. I am responsible of a Beekeeping Development Project in the Panama Canal Basin thru a USAID grant.

I am very happy reading about the palo blanco. This plant is important for honey production. Recently we harvested honey from palo blanco at an apiary site in Nuevo Ocú area. It has a great taste and character.

My family owns a beekeeping business at Chiriqui Province (West border). We manage 3,000 beehives.

In the past we gave logistical support to a STRI project regarding to plants visited by bees: Estudio Apibotánico de Panamá. David Roubik and Bob Schmalzel.

This plant is found in the Paraguay River at El Pantanal area, Caceres, Brazil in the border with Bolivia. The honey taste the same as in Panama.

When our own palo blanco was in bloom, I saw bees around the flowers, just as I’ve seen bees around many other plants in bloom. It never occurred to me that the honey from these aster family flowers might have “great taste and character,” in Juan’s words.

Let this message be a heads-up to potential beekeepers in Panama!

It still surprises me that there are so many members of the composite family (Asteraceae) in the tropics. It should not be surprising – the aster family and the orchid family are the two largest families of flowering plants. But somehow I feel the orchids belong in the tropics and the asters belong in the temperate world.

Even wikipedia says that although the aster or composite family is cosmopolitan, it is more common in the temperate climate and in tropical mountains. Nevertheless, the tropics are loaded with members of the aster family. Here in the western hemisphere, in the neotropics, we have 580 genera and 8,040 species of composites. By contrast, we have 300 genera of orchids and 15,000 species. (Statistics from Maas.) So, we have more species of orchids, but we have more genera of composites. Not as clear-cut as I previously thought.

Here in the savanna, in the dry season, the composites are conspicuous. We even have trees in the family Asteraceae – four of them are listed in the Trees Atlas of Panama.

One of those trees is the palo blanco – a brittle tree that suffered quite a bit of damage during the recent high wind episode.

Its scientific name is now Vernonanthura patens, although in its botanical history it has had at least six other names, one of which was Vernonia patens. The only complete description I’ve found for palo blanco is one in the Flora of Panama (Part IX. Family Compositeae), when it went under the name Vernonia patens. So I’ll be going through that description to show how to recognize the palo blanco, or Vernonanthura patens.

Vernonanthura patens is a Shrub or Small Tree to 8 m Tall

This young tree is no more than about 2 m tall, but I have seen them much taller, some on our own property, and one along the road to David that surely exceeded 8 meters – it seemed nearly 50 feet (15 m) tall.

The tree is “freely branched.” See how open and free the branches are in this young palo blanco. The branches themselves are marked with fine, usually parallel lines or grooves. You can see more freedom of branching in the image on the left, below, and the fine lines show up pretty well in the image on the right, especially when you click to enlarge it.

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If I were taking a course in botany, I’d be lucky if I were averaging a “C.” I am still too eager to get to an ID – I’d like to know a name, a family, something about the plant, and move on.

This attitude gets me into trouble. I zero in on a feature or two and think that is sufficient information to tell me what the plant is. Almost inevitably, I’m wrong.

Case in point. When I returned from my annual visit to the U.S., a small tree was in bloom near my favorite nance tree.

I took pictures, looked at the plant, even sketched a bit of it. Then I went to Keller’s key for identifying plants based on vegetative characteristics. I followed the features – I thought – down to a family I had never heard of, but which sounded very interesting. Feeling sure of myself, I sent off some images and my idea of an ID to a botanist at the Field Museum in Chicago who has helped me before. Almost by return email he kindly informed me that I was entirely wrong – that my plant belonged to the Asteraceae family (the Aster, or Sunflower, family), and that it was probably what used to be called a Eupatorium, the genus of Boneset and, at least formerly, Joe-Pye Weed.

I was stunned and humbled. How could I have made such a mistake?

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I never thought I’d use the genus and species name of a plant for my title with such confidence (95%, as they say). But here it is.

[A high resolution image is here. ]

Tithonia is named for Tithonus, a Trojan in Greek mythology who was allowed to be immortal but was not granted eternal youth and who, after becoming very ancient, was turned into either a grasshopper or a cicadia. The species name, rotundifolia, means “round leaf,” which would shake my confidence in the scientific name if I didn’t have lots of other criteria for deciding on it. You’ll find picture of the leaves after the break.

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