The orchid stems can grow to 3 meters tall, and the flowers are at the very top, so their gradual leaning over the past week or so gave me the chance to take some images of the lovely flowers.

Panama is home to no doubt hundreds of species of native orchids, and Potrerillos has a particularly fine climate for them, but the first orchid I decide to write about, this one, was introduced from Asia! My excuse is that this orchid is highly conspicuous, being very popular as a cultivated plant. It’s been introduced to Puerto Rico, Costa Rica, Guatemala, and Panama, according to wikipedia, for this purpose. I had to wonder what the chances were that it would become an invasive plant.

If you don’t live in our neighborhood, and you’ve seen these orchids, you may very well know them as “bamboo orchids.” They are reminiscent of bamboo, with their reedy stems, formation of large clumps, and fairly tall size. Their scientific name is Arundina gramnifolia.

• Arundina comes from the Latin arundo, meaning reed,
• and gramnifolia means grass-like leaves (botanary).

So let’s take a closer look at these reedy stems and grass-like leaves.

If you saw this plant without its obviously-orchid flowers, how would you know it was not a bamboo or some other member of the grass family?

• The leaves are long and narrow – like grasses
• The leaves have sheaths that clasp the stem – like grasses

There are, actually, quite a few differences in the leaf structure between the orchid and the grasses if you look closely, but the easiest way to tell this plant is not a grass is by checking its stem.

• Grass stems are hollow.
• This stem is quite solid.

By vegetation alone, then, we can see that it is not a grass. It’s the flowers that tell us it is an orchid.

Arundina flowers

Even though we usually see only one flower at a time at the tip of a tall stem, the flowers occur in clusters, though of not more than 10. You can see the buds for new flowers here.

Arundina flowers, like all orchid flowers, have an outer whorl of 3 sepals and an inner whorl of 3 petals. The petals and sepals generally look so much alike that in the orchid world both sepals and petals are called tepals.

In the images below the flower is face down. The sepals are labeled in the left image and have been removed in the right image. (Click on either image for a larger view.)

When you remove the 3 sepals, you are left with 3 petals, but it looks like 2 petals plus another flower! This is a characteristic orchid structure. The middle petal is called the labellum, or lip, and it is always different from the others and larger than the others. It ends up at the bottom of the flower and provides a platform for orchid pollinators (wikipedia).

The next two images show (at left) the petals turned over so you can see the labellum and (at right) the labellum opened up so you can see the yellow-streaked platform highway for the pollinators. (Click on either image for a larger view.)

Okay, then what is that phallic-shaped space module in the middle of the labellum? Oddly enough, it’s, to oversimplify a bit, the male reproductive part of this orchid – the column that carries the packages of pollen, the pollinia, discussed recently here. Without consulting an expert, I’m certainly not going to try to label the parts of this incredible structure, but I think the pollinia are stored in the little cap-bill of the column pointed to by the arrow.

At least, when I touched that part of the column with my finger-tip, it fell off fairly easily. If the pollinator has followed that yellow streak pathway up toward the column, it wouldn’t take too much effort for that cap-bill to detach from the orchid and attach to the pollinator, in my viewpoint, anyway.

So, what pollinates Arundina, and what does the pollinator get in return?

From a study in Puerto Rico, where Arundina graminifolia has become naturalized, and also from Zuchowski in Costa Rica, I would expect bees to be the pollinators here in Panama. However, at the time I was taking pictures, anyway, I saw only ants, some other tiny unidentified insects, and this lightning-bug type guy.

I wasn’t sure the bug was serious, but pretty soon, I saw this:

There he is, traipsing right up the pollinator highway. And what will he get for his efforts? Well, no nectar, that’s for sure. Arundina is what is known as a “rewardless” orchid. Perhaps in this case, fair is fair, because it’s hard for me to see how those pollinia would find a surface on this insect’s body, anyway.

Is Arundina gramnifolia invasive here?

Getting back to that original, idle question – it turns out that this “rewardless-ness” is one of the reasons this exotic plant from Asia may never become an invasive species here in Central America. Studies in Puerto Rico showed that although Arundina graminifolia had become naturalized there, the infrequency of pollinator visits (no nectar reward, why visit?) meant infrequent fruiting and therefore the orchid spreads in its new environment at a rate similar to native species.

You may have been able to answer immediately because you are very familiar with all three kinds of flowers, but what was it about this one that told you what it is? If you didn’t know what it was, don’t worry, the answer will be given later.

Orchids, lilies, and irises each belong to a different family: Orchidaceae (22,000 species), Liliaceae (1600 species), and Iridaceae (1500 species), respectively. Each family is widely distributed throughout the world. (Click on any image to enlarge.)

The flowers are so showy and beautiful that they’ve been thoroughly cultivated, and if you’re at all familiar with flowers, you can probably easily distinguish any of the three cultivated flowers. But what if you happen upon one in the wild?

It happened to our friend and naturalist, Michael. He sent around an image by email asking for guesses about a plant he found growing near his new home. He thought it might be an orchid but wasn’t sure. Our friend Carla responded with the tip that prompted this post (tip used by permission):

Peek straight into the center of the flower and look to see if it has long filament-like stamens holding pollen conspicuously on the tips. If yes, you might have a lily.

An orchid, however, would have a solid column holding two or more solid masses, called pollinia, which stick to pollinators, probably on the upper side of the throat.

What a simple and straightforward tip! So let’s look.

I couldn’t find a good image of a Tiger Lily (to keep the theme of the leopard-spot flower in the original image) that was not copyrighted, but here’s a lily that was blooming in our yard in early June this year. Click to enlarge or click on Hi-res for higher resolution options.

Hi-res

Nice long, filament-like stamens (male reproductive parts) holding pollen conspicuously on the tips (nothing more conspicuous than black pollen against a white petal!)

Now, let’s compare it with a much smaller orchid that bloomed in April of this year and that keeps the leopard-spot theme (no reason to do this, just fun). The image is a bit fuzzy – I can’t remember if the wind was blowing or whether I had a shaky hand that day – but you can tell that the interior of this flower does not resemble a lily in the least.

Hi-res

There’s the solid column holding two solid masses, the pollinia. As you might have guessed from Carla’s tip, the pollinia are carried away en masse from the flower. No dithering around with small pollen grains here.

Okay, so Carla’s tip had to do with orchids and lilies. Why did I bring in irises? Because when I went outside to start seeing for myself what Carla’s tip was all about, I saw the mystery flower at the beginning of the post. It’s an iris, and when I peek inside I see something a little bit in between the orchid and the lily.

Hi-res

The stamens are not long filaments with the pollen conspicuously at the ends. They are thick and the black pollen grains are on the side rather than the end. Notice that there are only 3 stamens, not the several we find in lilies. This is one of the distinguishing characteristics between lilies and irises. It may not be so easy to tell that these pollen grains are not glued together into pollinia, but if you were to take this flower apart, you’d see that there are 3 distinct stamens, not the one column that you see in orchids, and you’d see the individual pollen grains crumble off.

So there you have it. A simple way to tell lilies from orchids and even from irises. In short:

• Lilies have long stamens with conspicuous pollen at the ends.
• Irises have only 3 stamens.
• Orchids have one column supporting two or more packages of pollen called pollinia.

The answer, then, to the question at the beginning of the post is: you can tell that this flower is an iris because it has 3 stamens and no pollinia. And, by the way, Michael’s flower was an orchid.

Other differences, of course, can be found among these three families, but these differences are fun and useful, in my mind.

Update: The iris has a scientific name! It was recognized as Neomarica longifolia by user tem0dium on Flickr. With that head start, you can expect a closer look at it sometime in the future.