Elm-leaved Turnera – Turnera ulmifolia

The other day while walking through the nearby pine plantation, I looked down upon a nice sight.

I’m poorly prepared to identify wildflowers, but this one was so attractive that I thought surely it would be in one of my books. Even there in the woods I could see that it was a non-woody plant (an herb) that had

• simple, alternate leaves with toothed edges
• leaf veins in a feather pattern (pinnate venation)
• flower solitary (not a part of a flower cluster or inflorescence)
• 5 slightly fringed petals and 5 pollen-bearing stamens.

I took a cutting home to look at the details more closely.

The leaf blades were about 5 cm by 2.5 cm long.

Hairs on both top and bottom gave the leaves a velvety feel. More interesting was a feature that I thought would really help in identification – two small glands at the base of the leaf blade. If you look closely, you’ll see smooth little nodules – like tiny Lima beans – at the exact place where the leaf blade meets the leaf stalk (petiole). There’s also an oval-shaped structure right at the base of the petiole.

I also managed to look at the flower itself more closely. It had 5 sepals and 2 grass-like small bracts (bracteoles). Further, its 5 pollen-bearing stamens hid the one female pistil.

In my naivete, I assumed that this information would suffice for me to at least discover the family to which it belongs. Brother, was I wrong!

Stumbling toward an identification

Because I have no book specifically on “tropical wildflowers” or other guide that deals with non-woody plants, I tried two very broad and general keys on the internet. From them I obtained long lists of possible families. When the plant was later identified, I found its family did not even appear on either of these lists. Either I made errors in working my way through the keys or the keys themselves were simply too general to be useful.

So I turned to a source that has been useful before. Many amateur and professional botanists are members of the photo-sharing site, Flickr, and many of them participate in a group called “What plant is that?” If you join the group, you can post an image to it and often within the day someone will have helpfully identified your plant for you.

And so it was that Flickr member Tony Rodd named the plant: Turnera ulmifolia. Now all I needed to do was to find out to which family it belonged and then to learn what characteristics made it a member of that family.

Turner ulmifolia belongs to the family Turneraceae

The genus Turner (and hence the family Turneraceae) is named for William Turner, who published the first original botanical work in English in the 16th century (Botanary). With the publication of the two volumes, it was possible for the first time for ordinary, nonprofessional people to “…identify the main English plants without difficulty” (wikipedia).

Turneraceae is a small family, consisting of 120 mostly tropical and subtropical species in 10 genera, and the largest genus in the family is, not surprisingly, Turnera, to which half the species belong (wikipedia).

Characteristics of the Turneraceae family include (from Flora of Panama, Part VI. 1967. Ann. Mo. Bot. Gard. 54(1):85-94).

• herbs or shrubs, infrequently trees
• simple, alternate leaves, often with 2 glands at the base of the leaf blade
• flowers mostly solitary
• 5 sepals, 5 petals, 5 stamens
• other flower features:
  1. usually with 2 small bracts (bracteoles)
  2. the flower stalk (pedicel) may be fused to a leaf stalk (petiole)
  3. hypanthium (we’ll get to this later – for now think “rose hip”) usually present

Comparing this list with my earlier list from field observations:

• herb (check)
• simple, alternate leaves with toothed edges (check)
• leaf veins in a feather pattern (pinnate venation) - no mention of this in the description
• flower solitary (check)
• 5 slightly fringed petals and 5 pollen-bearing stamens (check)

Four of my field observations matched. I found the two glands at the base of the leaf blade and the two small bracts after I got back to my work table. The remaining two characteristics took a little more work. Here they are again:

1. the flower stalk (pedicel) may be fused to a leaf stalk (petiole)
2. hypanthium usually present

When I first read “pedicels . . . adnate to the petioles of the subtending leaves,” which is how the first feature is described in my reference, my eyes sort of glazed over and I thought I’d have to come back to that feature a little later. Luckily, another botanical member of Flickr – one who is also (I learned from a commenter) a leading palm systematist based at Fairchild Tropical Gardens in Miami – scott.zona, commented on the image of the leaf showing the glands and the leaf stalk.

Here’s what he said:

I think the “unknown structure” on the upper (adaxial) side of the petiole is the inflorescence bud or scar (depending on whether the plant has not yet or already flowered). As you’ve surely noticed, the inflorescence in T. ulmifolia is fused to the petiole. The flower appears to originate from the leaf (but we know leaves can never bear flowers).

What an education in those three sentences! First, he identified the “unknown structure” as a scar. Second, he gave me undeserved credit for noticing that the flower stalk was fused to the petiole, a characteristic of Turneraceae, which would cause the scar. Third, he mentions the botanical fact that leaves cannot bear flowers.

So that takes care of

• the flower stalk (pedicel) may be fused to a leaf stalk (petiole)

Now for

• hypanthium usually present

Probably any botany student learned what a hypanthium is when they studied the rose family. It is “an enlargement of the floral receptacle bearing on its rim the stamens, petals, and sepals and often enlarging and surrounding the fruits (as in the rose hip)” (Merriam-Webster’s Online Dictionary). Being a self-taught botany student, I had not thought about hypanthiums at all when I first looked at the flower. I needed to go back and look again.

My first look at Turnera ulmifolia was in May. It is now mid-June and I wasn’t sure I would find a plant in bloom. I didn’t, exactly, but I found either a flower that hadn’t opened yet or one that had already closed and I managed to find the hypanthium. While looking, I also saw ants sucking nectar out of the glands at the base of the leaf – showing how they function as nectaries. The quality of the photo leaves something to be desired, but I was happy to find two features for the price of one. If you’re serious about seeing these features, you’ll need to click to enlarge, or better still click here for the Flickr image at the best resolution I could get.

Now that the plant has shown itself to clearly belong to the Turneraceae family, what makes it a member of the Turnera genus?

Panama’s Turneraceae

There are three genera of Turneraceae in Panama, and they’re easy to distinguish. (Both the genus characteristics and the species characteristics are taken from the source listed earlier: Flora of Panama, Part VI. 1967. Ann. Mo. Bot. Gard. 54(1):85-94.)

1. One genus consists of trees, and the flowers in these trees have no hypanthium (Erblichia).
2. One genus has a corona, or crown, in its flower (Piriqueta.)
3. One genus has no crown in its flower (Turnera.)

This plant is not a tree, it has an hypanthium, and it has no crown in its flower, so it belongs to the genus Turnera.

Panama’s Turnera

There are three species of Turnera in Panama, and they, too, are pretty easy to distinguish.

1. Leaf blades have no glands at the base. (T. panamensis, found only in Panama)
2. Bracteoles leaf-like and egg-shaped, 15-30 mm long (T. angustifolia – a shrub found on the Atlantic coast, often considered a variety of T. ulmifolia).
3. Bracteoles linear to awl-shaped, 10 mm long (T. ulmifolia).

So, once the plant has been placed in the correct family, it’s quite simple to find the Panamanian member of that family. No crown in its flower and linear, short bracteoles are all we need to know to say with confidence that it is Turnera ulmifolia.

Ecology

Remember those glands at the base of the leaf blade? These are “extrafloral nectaries,” used by wasps and ants on Turnera ulmifolia. These two nectar eaters help protect the plant from its main herbivore, the caterpillar Euptoieta hegesia. If the wasps or ants are present on the plant, it produces more buds, flowers, ripe fruit, and seeds than it would if the wasps or ants were not present (Cuautle & Rico-Gray).

The ants perform another function as well – they disperse the seeds of the fruit. Since the ants do not carry the seeds very far, dense local populations of T. ulmifolia can be established (Barrett).

I’ve seen the ants, but not the wasps nor the caterpillar. Still, I’ve seen two insects that I could not resist trying to photograph: 1) a green something that looks to my untrained eyes like a very young grasshopper and 2) a black something busy on the stamens, maybe eating pollen, reminding me of the weevils on Davilla.

A note about the common names

All the common names, except the last one, listed in the table at the beginning of the post come from the ZipcodeZoo site. The one exception is from Curtis’s Botanical Magazine, and that exception – Elm-leaved Turnera – is the one that makes the most sense to me, who grew up in the northern hemisphere among elm trees. Of course, if you look at the leaves again, “Yellow Alder” makes good sense, too.

When I first saw the common names given at several sites for Turnera ulmifolia, I was hoping to title this post “Ramgoat Dashalong,” a nearly irresistable common name. However, a wikipedia article convinced me that such a name more properly belongs to another Turnera species known for its aphrodisiac properties, T. diffusa, synonym = T. aphrodisiaca. So, for me at any rate, Elm-leaved Turnera it is.

In summary, then, the plant Turnera ulmifolia is a member of the family Turneraceae, which is characterized by simple, alternate leaves often with two glands at the base of the leaf blade, mostly solitary flowers with 5 sepals, 5 petals, and 5 stamens, two bracteoles, and an hypanthium. The flower stalk may be fused with the leaf stalk. The family is small and is found mostly in the tropics and subtropics.

Turnera ulmifolia is one of three species of Turnera found in Panama. Ants and wasps feed at its extrafloral nectaries, and ants disperse its seeds.