Bamboo Orchid, Arundina graminifolia

What you see on the left are a stand of what we call soil orchids, some of which have been beaten to the ground by heavy rains, and on the right a stand of robust Curcuma (locally, resurrection plant) leaves. The orchids have been straining toward the light for some time – we had no idea the Curcuma would cast so much shade when we planted it there – and the rains just helped them plunge on down to the ground.

1 Fallen Orchids

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.

2 Arundina Flower

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.

3 Arundina Stems

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.

5 Arundina Solid Stem

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.

6 Arundina Cluster

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.)

7 Arundina Sepals8 Arundina Petals

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.)

9 Arundina Petals210 Arundina Lip

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.

11 Arundina Column

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.

12 Arundina With Beetle

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

13 Arundina Beetle

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.

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57 Responses to Bamboo Orchid, Arundina graminifolia

  1. G A Lambert says:

    I forgot to mention that when pruning be careful not to snap off the new shoots as they are very easily broken. So it’s also easiest to remove the old canes when the new shoots are just five cm or so, take the old canes off as low as you can reach the old cane will not regenerate or send up a new cane but die and is easily pulled out when they soften and turn straw like.

    This species “Arundina graminifolia” is a mainstay in many spectacular tropical gardens, planted in raised beds en masse like they do at the famous Singapore Orchid gardens. The long season compared to most other orchids and the attractive upright growth of the canes make it indispensable.

    Sandy poor light soil means the roots grow very healthily and big and so they make large healthy abundant sturdy canes and many flowers, heavy clay and or rich soils mean they grow a bit too tall and thinly and the roots are either restricted not making much of a good thick clump or many flowers at once or they grow too high with much vegetation and hardly any flowers and fall over. But either way they are survivors and the soil is easily made accommodating.

  2. Bill says:

    What do I do to get them to flower? Thanks. Bill

  3. G A Lambert says:

    I found a beautiful form of this a few weeks ago on Sabah Borneo growing at good altitude where the weather is constantly cool and misty. The canes are very thick at the base (3 cm) and growing tall and tapered, to an extent that I think this might be a different Arundina species as it’s very different truly a giant one. The flowers are intense red/pink or hot pink uniform over the entire flower. Interestingly the flowers do not drop but remain even when the pod is fully mature, like a petticoat at the tip.

    There is also a Vietnamese one which is very short and has lovely completely dark glossy purple flowers with a red throat. I don’t have this one.

    Im always a bit puzzled at why no work has been done on this species by way of hybridising and improvement of flower size different colours etc. Its such a nice and easy form in growth, long flowering with the added advantage that it’s a terrestrial , it really is strange.

  4. mary says:

    Fascinating. I’ve never seen this plant in cool and misty conditions here in Panama.

  5. Arteel Roger says:

    Dear sir;
    Iam looking after fresh seeds of Arundina -graminifolia ,Who can help:
    and what is the price + send cost, or a address where I can find; my hobby is medicinal plants ,have so one 220 sort,as nature man ,not sell plants,
    greetings Roger

  6. kim says:

    I am in Hawaii and I have transplanted a few plants around my house. They took close to 2 years before they bloomed. But once they take hold I have blossoms year round. Thank you for the information.

  7. G A Lambert says:

    And at long last!!!! A few weeks go I was in Thailand, and it appears that some ‘work’ is being done with these long neglected fabulous orchids, to both increase flower size and forms and colour.
    I was able to purchase some very nice dark dark all purple ones with a deep red throat and a glossy sheen to the petals, and one white with dark purple trimmings around the lip and petals, very striking large spidery blooms.
    There is one I have seen on the internet and if anyone reads this Im dying to get hold of some of it, so far no luck as the site was a Thai orchid forum in Thai where I saw it. Its pure crystline white all over except it has a dark reddish purple throat. I think its stunning.

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