So I was curious. It’s certainly not the Salvia in the mint family that we know from the Northern Hemisphere, but the leaves are a little reminiscent of sage to the touch. What plant is it, then?

After I saw the one that fell, I learned to recognize the mature tree. It has a trunk that reminds me of one of my favorite savanna trees – Miconia rubiginosa.

Having the images here side by side, I see that the trunks aren’t all that similar. The grooves of the “salvia” on the left are lighter in color and straighter than those of the Miconia on the right. Nevertheless, the bark in both cases is deeply grooved and the trunks of the mature trees are roughly similar diameters.

In an abandoned pasture, the “salvia” is likely one of the tallest of the trees there, but if it’s growing along side a quebrada (a spring, sometimes seasonal) it’s just one among other tall ones. When in bloom, it’s possible to see that the flowers are white, but that’s about all you can tell from the ground. The flowers are high up in the crown of the tree, impossible to reach.

I decided my only hope of seeing a flower close-up would be to wait until our sapling matured enough to bloom, with luck while it was still short enough for me to reach the flowers.

This year, 21 months after the first picture of the sapling was taken, it looked like this, and the top is out of sight – threaded into the nance tree (Byrsonima crassifolia) the sapling is beneath.

Quite a rapid growth, in my opinion, but not rapidly enough to produce flowers. Nice leaves, though, don’t you think?

Fortunately, another young tree nearby did have some flowers:

Enough to confirm my suspicion that this tree belongs to the aster family (Asteraceae).

I admit I groaned a little. The Asteraceae family is huge and its flowers are tiny. The flowers are so special they have their own terminology. The terms I’m about to use were gleaned from a wonderfully helpful page on the Flowers of Asteraceae at PlantzAfrica. What is shown in the image above is a cluster of synflorescences. One of them needs to be broken down a little so you can see what that means.

Here is a single synflorescence on the left. From it I plucked a head, or in Asteraceae terminology, a capitulum, which is next to the ruler. The capitulum is a small inflorescence or flower cluster. In this case, the cluster of flowers consists of two tiny flowers called florets. So a synflorescence is, you might say, an inflorescence of inflorescences. Perhaps a “compound inflorescence” would be a better term.

There’s a great deal more to the terminology, but this is enough to confirm that the plant belongs to the Asteraceae family. If I had to identify this plant based on a dissection of these tiny heads, I’d be in trouble. But I figured I could possibly get around the problem by holding in my head that this plant is a tree.

There aren’t that many trees in the Asteraceae family.

So I took a deep breath and pulled out my copy of Gentry’s field guide and plowed into Asteraceae. He listed 19 genera that contained trees, and I was preparing myself to read up on all 19 when I came across this description for the genus Pollalesta on page 349:

Medium-sized second growth and savanna trees with corymbose panicles. Leaves densely gray-pubescent below.

The accompanying illustration was promising. And yes, this is second growth in these pastures of the savanna.

Botanical side note: [definitions from the New Oxford American Dictionary]

• corymb = a flower cluster whose lower stalks are proportionally longer so that the flowers form a flat or slightly convex head. corymbose = adjective.
• panicle = a loose, branching cluster of flowers, as in oats.
• pubescent = covered with short soft hair; downy

This is what it’s often like for me – look up every third word or so in a description! Some of the terms are beginning to stick, but I despair of ever knowing them all. I do use a reference other than a standard dictionary, though. The book by Harris and Harris gives real botanical definitions and illustrates every term. It’s wonderful, but their definitions are a little too complex for my posts.

Next, I checked the Tree Atlas of Panama, and yes, trees of the genus Pollalesta are found here.

Next reference to check was Flora of Panama: Compositae [Compositae is the former name of the Asteraceae family]. Ah, success! Pollalesta is in Panama and it is represented by only one species: P. discolor. It’s enough to say that the description of the head (capitulum) fits and that there are two tiny flowers (florets) in the capitulum.

So, Pollalesta discolor it is. But wait. What’s this about Piptocoma discolor, the name in the title of this post?

Well, as happens fairly often in the plant identification world, a qualified botanist decided that Pollalesta was not really a separate genus but, on the traditional basis of the characteristics of the plants, should really be lumped together with the genus called Piptocoma. The only species in Costa Rica and Panama affected by this decision was Pollalesta discolor now called Piptocoma discolor. [Pruski] The complete official name now is Piptocoma discolor (Kunth) Pruski.

What is known about this tree, this Piptocoma discolor?
For one thing, it is found in abandoned pastures in Panama and Costa Rica, in dry to moist areas. It flowers in January and April and in November and December; it fruits in June, July, and December. [INBio]

It occurs from Costa Rica south into northwestern South America

In the province of Herrera here in Panama, it has the common name of negro [Spanish for "black"]. I suspect that name comes from the color of the inside of the bark, which is extremely dark. The Miconia rubiginosa tree that I mentioned earlier is known locally as canela negra, also, presumably because of the dark interior of the bark. In Herrera, at least, the Piptocoma is recognized as having some value in the pasture and so is not removed. It is said that its bark, pounded and mixed with water, gives a drink against snake bite. Don’t use that remedy on my say-so, though!

That’s about all I’ve been able to find about it. Not a popular tree, I suppose, except perhaps with our former gardener, Dario, and with me. I probably like it because Dario did, but you must admit the leaves are pretty, the bark is interesting, and it makes a nice tall tree in the pasture. I’ll probably never learn why Dario called it salvia silvestre, though.

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!

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.

The younger stems and twigs may be covered with short, matted or tangled, soft wooly hairs.

Leaves with Short Stalks; Leaf Blades Lance-shaped

The leaf stalks or petioles are so short it’s hard to remove the leaf from the stem. The leaf blade is longer than it is wide, with the widest part below the middle (this shape is called lanceolate). It is sparsely covered with soft, short hairs on top and with fine, short hairs that may be stiff on the underside.

There may be 8 to 20 pairs of lateral veins.

Flowers Occur in Terminal Clusters, Much-branched, with Slightly Convex Head

The flower clusters, or inflorescences, are at the ends of the branches (terminal) (left image below), and just as the tree is freely branched, so the inflorescence is freely, and much, branched (right image below).

This type of inflorescence is called a corymb, which means that the lower stalks are longer than the upper stalks so the flowers form a flat or slightly convex head (American Heritage Dictionary). You can see the different sizes of the stalks in the next image, especially if you click on the image to enlarge it.

Flower Heads have 21-27 Florets

If you look at a sunflower closely, before the seeds form, you’ll see that the center of the flower consists of tiny individual flowers. Even the part of the sunflower that looks like a petal is another kind of flower. This grouping of tiny flowers into a “head” is what gave the aster family its older name, the composite family or Compositeae.

In the case of palo blanco, there are 21-27 small flowers in each flower head.

The Involucre is broadly Bell-shaped

An involucre is a whorl or rosette of bracts surrounding an inflorescence, or in this case, a head of flowers. (From the Latin involucrum, from involvere, ‘roll in, envelop’.) Involucres are the single most distinguishing feature or the aster family. They look like miniature artichokes. One of the first things I do now when looking at a flower cluster is to look for those multiple layers of bracts at the base of the flower. If they’re there – it’s a member of the aster family. If not – well, there are lots more families to choose from.

The bracts in the palo blanco come in a series of 5 or 6, closely overlapping like tiles on a roof, and are pale green with brown midrib or tip.

The Petals form a Slender Tube with 5 Lobes abruptly Spreading

If you enlarge the labeled flower head above and also the one immediately below, you’ll see several individual flowers with their 5 petals. The slender tube with 5 lobes abruptly spreading is called a “salverform” structure.

You’ll also see several branched styles – part of the female reproductive system of the flower. These branched styles continue to develop until they take on a “ram’s horn” appearance, which is a characteristic of Vernonia-like flowers.

The male part of the flower’s reproductive system, the stamens, are hidden within the petals.

When you look closely at the enlarged images of the flowers, you’ll see tufts of hairs or bristles on the outside of the petals. These hairs are collectively called pappus and are another characteristic of the aster family. In the drawing of a Vernonia sp. from Delta-Inkey below, you can see the relation between the achene, which will become a small dry fruit with a single seed, the pappus, and the flower.

In the aster family, the pappus serves the same role as sepals in other flowering plant families.

Identification Summary

You can recognize the palo blanco, then, by

• it being a small shrub or tree to 8 m tall
• freely branched
• leaves with short petioles
• leaf blades lance-shaped
• terminal, corymb inflorescences
• 21-27 florets in flower head
• bell-shaped involucre
• 5 petals forming a slender tube
• branched styles

Distribution of Vernonanthura patens

This species is relatively common, extending from southern Mexico to tropical South America in the neotropics.

It is so common, in fact, that it is called a “weed” by the Germplasm Resources Information Network (GRIN). But as we all know, weeds are in the eyes of the beholder, and parts of palo blanco have been used to treat conjunctivitis, although without paying to see the entire article, I do not know which parts nor how effective it is. (Phytotherapy Research, Vol. 16, Issue 1, pp 1-22, 2002). Surely, also, its branches have been used as walking sticks or broom sticks – with a name like that.

What’s in a Name, Anyway?

The genus name , Vernonanthura, is named for 17th century English botanist, William Vernon. The species name, patens, means “spreading.” With “weed” still in mind, patens may refer to the ability of the entire plant to spread like a weed, but I’m guessing that the spreading refers to the tree form, which is rambling to say the least. The post began with an image of a nice, relatively compact young palo blanco. Here’s an older tree from our front yard.

Vernonanthura spreading.

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?

It was not the fault of Keller’s key. It was my own hurry, and my misreading of a couple of significant characters. But even if I had used the key correctly, and had been lead to the Asteraceae family, I might have at that point thought I was doing something wrong.

When I think of the Aster family, I think of sunflowers and daisies, and now, from here in Panama, the so-called Mexican sunflower, Tithonia, which was also in bloom when I returned from the U.S. “Aster” means “star,” and my mental image is of a sunflower – a kind of star of the prairie. The Aster family used to be called the Composite family for reasons that will become clear shortly, and a statement from Lady Bird Johnson has stuck in my mind all these years – a statement about the difficulty of identifying those “darn yellow composites.”

The pattern of most flowers
I went back to my very first botany book, Botany in a Day, by Thomas Elpel, to zero in on what it is that makes a plant a member of the Asteraceae family. As it turns out, flowers of the Aster family are more complex than flowers from almost any other family. The flowers of most families have, if you look down upon them:

• a ring of sepals
• a ring of petals
• a ring of stamens (male reproductive organs)
• a pistil or pistils (female reproductive organs) in the middle

A cross-section of most flowers would look something like this illustration from the Biology Department of the University of Cincinnati Clermont College:

The pattern of Asteraceae flowers
By contrast, flowers of the Aster family have:

• bracts (modified leaves) where you would expect sepals – often in multiple layers
• ray flowers (usually) where you would expect petals
• disk flowers in the middle – here at last are the flowers most like those found in other families, though tiny, with microscopic sepals, petals, stamens, and pistils

Hence, the flowers are really “composites” of different kinds of very small flowers – hence the earlier name, Compositae, for the family. You can get an idea of the complexity of the flowers of this family from the following diagram. It’s from a great web page on Dahlias from Stanford University.

Botany gets even more complicated, though, when you learn that some members of the Aster family have both ray and disk flowers, some have disk flowers only, and some have ray flowers only. So how do you know when you have an Aster family plant in hand? According to Elpel, it’s pretty straightforward: look for multiple layers of bracts beneath the flowers. Also, look inside the flower head for the presence of many smaller flowers.

So…here we go with my flower:

First, look at the “puffball” flowers on the plant:

Then, look closely at a puffball:

You can start to tell that the puffballs are made up of pretty small flowers. Let’s zero in and look for them and for those bracts:

There they are: 1) the presence of many smaller flowers, and 2) multiple layers of bracts beneath the flowers. (Those bracts look a little like miniature artichokes, don’t they? Yes! Artichokes belong to the Asteraceae family!)

Let’s try for a closer look at some of the flowers:

It’s clear from the Asteraceae drawing taken from the Dahlia page that there’s even more to the flower than this. But at least with the naked eye we can see 1) united petals – there are 5 of them to each flower, 2) united anthers – I only know this because of the location within the flowers; the male anthers surround the female pistils, and 3) two long, club-ended pistils, united from the tip of the petals down toward the bottom of the flower.

It used to be called a Eupatorium
Even with all this looking, I haven’t seen enough, or know enough botany, to identify the plant. The botanist at the Field Museum said it was probably “what used to be called a Eupatorium.” A “typical” Eupatorium was beautifully illustrated by John Curtis who was really painting bugs (British Entomology (1824-1835))- the link is at the DELTA description of the Compositae family, under Illustrations:

Before moving on, I’d like to look into that name. Dave’s Botanary says that Eupatorium is

Named for Mithridates VI Eupator, King of Pontus [a region on the south coast of the Black Sea, now in Turkey (wikipedia)] about 115 BC who is said to have discovered an antidote to a commonly used poison in one of the species.

A poison in one of the species. Hmm. Once upon a time, the genus Eupatorium was thought to have as many as 800 species. Now that number is down to somewhere between 36 and 60. (wikipedia) So which species Eupator found the antidote for is still unknown to me.

What’s happening in taxonomy
How the number of species in the genus got reduced by more than tenfold, though, is the story of what’s happening in plant taxonomy, or, more properly, plant systematics, these days. For many, many years, plants were identified by what they looked like – the shape and arrangement of leaves, for instance, the arrangement of the flower parts, and so forth – and by their chemistry – the color of the sap, for instance, or the aroma. The chemistry of plants may have been of primary importance to the very early botanists, because plants were looked to as sources of medical treatments. Early botanists tended to group together plants with similar medicinal properties. Many visible plant features corresponded with these groupings, so it made sense to rely on such external features in the absence of knowledge about medicinal properties.

In recent years, botanists have been trying to place plants in groups based on how closely related, in an evolutionary sense, they are. They are using genetic data, ecosystem data, distribution data (biogeography) as well as traditional chemical and morphological data. It is no longer just a matter of trying to find some order in the plant world and giving names to this order, which was more or less the thrust of taxonomy. It is a matter of looking at the whole system – hence, plant systematics.

This approach will be useful in the long run, and will really help us understand the plant world better, but at present it causes a great deal of confusion among those of us who are not professional botanists but who would like to know a little something about plant relationships. Whole families are being re-defined, the Aster family, formerly known as Compositeae, is one example. And the Eupatorium genus within that family is another example.

As redefined, the Eupatorium genus no longer is found in Central America. Indeed, the entire subtribe to which it belongs – the Eupatoriinae – are “virtually absent from Mexico through Central America.” (Schmidt & Schilling) This subtribe seems to be truly genetically related and includes Boneset, Joe-pye weeds and other genera found in North America and Asia.

The plants from Central America that used to be called Eupatorium have been moved to other genera, including Ageratina, Fleischmannia, Koanophyllon, and Mikania. (wikipedia) I mention these 4 genera of the 13 listed in wikipedia because they have been found either in Costa Rica or in Panama.

And there I must stay, hanging in suspense, not knowing the name of the plant until a kindly Panamanian botanist can take a look at my pressed sample.

Unidentified, but not unappreciated
In the meantime, I’d like to spend a moment with the plant in its entirety. The plant is growing in a cluster of other plants near my nance tree. I can imagine that the cluster there in that place arose from seeds in the droppings of a bird, a bird that sat in the branch of the nance tree.

Here are the flower head (inflorescence), the bracts, and the tiny flowers that make it recognizable as a member of an Aster family:

The leaves, stem, and trunk:

And, with a wink to John Curtis’s British Entomology, a bug among the bracts.

[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.

The leaves on this plant have two forms. The smaller ones are oval with a pointed tip and with toothed edges. The larger ones have 3 lobes. The leaf blade is “decurrent” on its stem, which means that the blade extends down the stem some from the point where it attaches. You can see this pretty clearly on the leaf to the right of the lower flower.

The characteristic that makes this plant a member of the Asteraceae family is, to use the words of Thomas Elpel: “composite flowers in disk-like heads.” (Elpel’s page in his Wildflowers and Weeds web site that describes the Aster family is a must-read for those who, like me, are new to plant identification and want to get acquainted this large family.)

The disk-like heads are made up of very small flowers, often called florets. The rays surrounding the disk are themselves flowers. In T. roundifolia, the ray flowers are golden with a tiny notch at the end.

In this image you can see both brown-black and yellow-orange florets. These are the anthers (male, brown-black) and stigmas (female, yellow-orange) parts. You may be able to see the details better in the high resolution image here.

The plant itself is a large shrub. I saw several shrubs on this roadside corner, but only one is pictured:

The reason I have such confidence in the scientific name of this plant is because a new and wonderful book has arrived in our household: A Guide to the Tropical Plants of Costa Rica by Willow Zuchowski. It’s 529-pages-worth of botanical, environmental, and social detail about the plants of the area. Since this neotropical savanna where I live is only a few miles from the Costa Rican border, nearly every page of the book has something familiar on it.

So I’ve learned, for instance, that T. rotundifolia is found mostly on the Pacific slope between 300 and 1,000 m (check – we’re at about 800 m), it’s an herb that grows as a shrub 1-4 m tall (check), it flowers along roadsides (check), and it flowers and fruits from late October through January (check – well, it’s not late October yet, but they did just start blooming). It may be coincidence, by the way, but I just read today that two Boston University professors have shown that flowers in the Concord area are blooming 11 days earlier now than they did in Thoreau’s time.

A final, nice surprise. T. rotundifolia is related to the Mexican sunflower (T. diversifolia), which has been used in Africa as a green manure crop. A brochure on how to use it is here. The differences between the two species are: the flower head of T. rotundifolia is smaller (about 7 cm across) than that of T. diversifolia (about 14 cm across), and the flowerhead bracts that form a cuplike receptacle are pointed in T. rotundifolia and rounded in T. diversifolia.