OrchidSafari ARCHIVES* Orchids that begin with 'T'

OrchidSafari
Orchid Genera whose names begin with T - Thunia and Trichoceros
Moderator: Marilyn Light
July 10, 2002

There is remarkably little in common between these two genera excepting that they are both orchids. Trichoceros is a terrestrial to epiphytic South American genus of about ten species allied to Telipogon and placed in the Maxillaria alliance. Trichoceros flowers mimic female tachinid flies which are parasitoids of other insects. Males seeking to mate with the floral mimics serve the flower instead of their own species. Trichoceros flowers have curious hooked structures at the base of their pollinia which get entangled in the feet of a visiting fly before it flies off in search of another potential mate. We have no photos of the fly species actually involved with the orchid but one suspects that each orchid species mimics a different fly. A typical tachinid fly is shown at http://www.bioimages.org.uk/HTML/P29284.HTM

Trichoceros growths have squat round pseudobulbs and 2 or 3 thick succulent leaves with shoots joined together by long internodes. Masses of aerial roots are produced by the epiphytic species. They form mats of growths in natural habitat and must be raised mounted on large slabs of bark if their spreading growth is to be accommodated. The curious flowers are carried on long slender inflorescences and open sequentially over several weeks. The center of the flower looks like a fuzzy insect. Trichoceros tupaipi (Peru) is a terrestrial with dull yellow, purple veined flowers and a purple column. More frequently seen are the dull yellow and burgundy flowered T. antennifer and its close allies which are often misnamed, and T. muralis whose flowers are distinctly pink. A newly described species from Peru, T. hajekiorum, has exquisite wine veining on pink. http://www.peruvianorchids.org/gc770.htm When examining Trichoceros flowers, pay careful attention to the shape of the lip, petals, and the overall insect-like form. Insect visitors are like very particular in their selection of a pseudomate and can discriminate between shapes and possibly also color patterns. Trichoceros plants are adapted to periods of dryness. They should always have good drainage and aeration between waterings.

Thunia is a small Asian terrestrial to lithophytic genus allied to Coelogyne and consisting of some five often misidentified species. The genus was named in honor of Count Thun of Hohenstein, Thunia marshalliana and T. alba are the most commonly encountered in collections. The plants are seasonally deciduous, They produce leafy canes which soon develop a dense cluster of six to eight large, showy white flowers at the tip of the new canes. The flowers, which smell of oranges, have an ornamented orange red lip. Blooms last two to three weeks after which time the canes gradually swell and mature. Flowers likely attract pollinators by scent. Thunia foliage is an attractive grey green and the mature canes smooth making this a very attractive plant when not in bloom. Leaves do eventually yellow which signals a grower to reduce watering. Once dormant, canes can be hung upside down in a warm greenhouse until the following spring when the plants should be repotted. Thunia can be vegetatively propagated by laying mature canes on dampened moss when offsets will develop at the nodes. Once offsets have developed roots, they can be removed and potted separately.

Discussion Begins:

MarilyninOttawa
This session we will be discussing two genera whose names begin with 'T'. There is remarkably little in common between these two genera excepting that they are both orchids. Trichoceros is a terrestrial to epiphytic South American genus of about ten species allied to Telipogon and placed in the Maxillaria alliance.

Trichoceros flowers mimic female tachinid flies which are parasitoids of other insects. An example is shown with a flower of T. muralis. The center of the flower looks like a fuzzy insect. This is a picture of a T. muralis flower. You will note that the flower has a strong reddish tone. This varies between plants. The petals look like wings and in this species are quite reduced in size.

Males seeking to mate with the floral mimics serve the flower instead of their own species. Trichoceros flowers have curious hooked structures at the base of their pollinia which get entangled in the feet of a visiting fly before it flies off in search of another potential mate. We have no photos of the fly species actually involved with the orchid but one suspects that each orchid species mimics a different fly. A typical tachinid fly is shown at [http://www.chaparraltree.com/mn/tachinid-3qf-med.shtml] The fly shown may not at all resemble those involved in Trichoceros pollination but gives you an idea of how fuzzy they can be.

The flowers of most species I have seen are about 1/2 inch or about 1 cm tall. Trichoceros growths have squat round pseudobulbs. The image is not in focus I know but I think you can get the idea of what the pseudobulbs look like. There are nice plants to look at! Each growth has 2 or 3 thick succulent leaves. Shoots joined together by long internodes.

Trichoceros grow over a wide range of altitude. Some are cooler growing than others but they are not particularly cold growers in general.

Masses of aerial roots are produced by the epiphytic species like T. muralis. They form mats of growths in natural habitat and must be raised mounted on large slabs of bark if their spreading growth is to be accommodated. When you look at the specimen plant, you will appreciate just how massive the plant can become. Almost a hundred growths covering a plaque about 3 x 2 feet is what we see here. The plant is not mine but I suspect at least ten years from the time it was acquired as probably a foot square division. We could see the original part where it joined the newer slab of cork.

The curious flowers are carried on long slender inflorescences and open sequentially over several weeks. We saw the same flower (different view) earlier.

Now we will look at some other species. I am uncertain as to their identification. All I know is that the flower structure is different which suggests that they are different species which merely look alike in color.

Trichoceros plants are adapted to periods of dryness. They should always have good drainage and aeration between waterings.

Trichoceros tupaipi (Peru) is a terrestrial with dull yellow, purple veined flowers and a purple column. More frequently seen are the dull yellow and burgundy flowered T. antennifer and its close allies which are often misnamed, and T. muralis whose flowers are distinctly pink.

A newly described species from Peru, T. hajekiorum, has exquisite wine veining on pink. When you look at the Peruvian species, bookmark the site for a more leisurely visit. Lots to learn there.

When examining Trichoceros flowers, pay careful attention to the shape of the lip, petals, and the overall insect-like form. Insect visitors are like very particular in their selection of a pseudomate and can discriminate between shapes and possibly also color patterns. Here is a flower that was labelled Trichoceros muralis but you can see that it is not only differently colored but the petals are differently shaped.

The yellow/purple combination seems to be quite variable in pattern but consistent across a range of species, excepting the pink/wine ones of course.

Another labelled T. parviflorum is similarly colored but differently shaped. I suspect that all flowers shown are different species.

John_in_Arcadia_CA
These plants seem to be cool growing judging from the altitude of that last one. True? So there might be hope for my conditions with temps up to 85?

MarilyninOttawa
I agree that the newly described species is high altitude and likely very cool growing. I would suggest cool to intermediate overall. I believe that consistently high temperatures would be detrimental but that some higher temperatures would be tolerated. The challenge will be if plants stressed by heat succumb more readily to rot. I would be scrupulous about drainage, air movement, etc.

Here is another T. muralis image [button] muralis pic For the some five to ten species, there is a lot of interest in these plants and their intriguing flowers.

I would love to see just what fly species are involved in pollination. There is a growing appreciation of just how complex some interactions are in anture. Here we have a flower dependent upon a fly which is dependent upon another insect as prey.

We will now move on to Thunia.

When I bought this plant years ago, it was a few dry canes - dormant. I was intrigued by the plant structure - sound familiar? Anyhow, I planted it, watered it, fed it, placed it in my greenhouse, and was rewarded in six short weeks by the flowers you have seen. I was amazed and inspired... they smelled of oranges!

The flower lip is deeply fissured and folded or so it appears.

The flowers, which smell of oranges, have an ornamented orange red lip. Blooms last two to three weeks after which time the canes gradually swell and mature. Flowers likely attract pollinators by scent.

Thunia foliage is an attractive grey green and the mature canes smooth making this a very attractive plant when not in bloom. Leaves do eventually yellow which signals a grower to reduce watering.

Once dormant, canes can be hung upside down in a warm greenhouse until the following spring when the plants should be repotted.

Thunia can be vegetatively propagated by laying mature canes on dampened moss when offsets will develop at the nodes. Once offsets have developed roots, they can be removed and potted separately.

Flowering size Thunia canes would be about min. 2.5 feet. If you feed and water adequately while the canes are growing, you can push another 6 in to a foot. The bigger the canes, the more flowers that year and the next. Canes are biannual, flowering the first year and acting as a storage organ the next.

Thunia can be a challenge to grow well. It must be dormant for a while then grow actively for only a very short while. It is susceptible to freezing.

I raised some plants from seeds...easy! The seeds matured in about six months, seedlings grew rapidly.

There is always something new to learn about orchids. I am happy that you are enjoying the pictures as well as the explanations. I have learned more also.

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