Oncidium nudum

[euplusia]

Vegetatively not to be kept apart from Oncidium cebolleta (3rd photo), this plant with terete leaves originates from hot savannahs or woodlands in the north of South America. It is sensitive to humidity and cold water in winter.
Some people call it now Trichocentrum, but I don't want to follow.
The golden flowers smell of marguerites (oxeye daisy, Leucanthemum), mothball or my grandmothers wardrobe, not bad from a little distance.

[stefpix]

Just saw a bunch of these (probably cebolletas) in teh Yucatan peninsula. It is a relatively dry jungle. Some were growing in really deep shade, almost at ground level with a thick canopy above. I think the terete leaves are more for storing water than an indicator of high light. Some were blooming in relatively shaded areas (the ones in deep shade were not blooming). I saw a few in open areas that were cultivated in a sunny spot and the leaves were red. But best orchids I saw there were in area protected from strong sun. How do you grow this? when does it start new growth? nice blooms and many!
(i have some photos in the orchids in the wild forum)

[tucker85]

Is this one of the Trichocentrums that was known as a mule ear oncidium before? I have a couple of Trichocentrums that I like but yours has more colorful flowers than the varieties I have. It's interesting to hear about it growing in deep shade because there seems to be some confusion over how to grow these.

[stefpix]

If you scroll down here you can see some orchids ina nursery in a forest clearing

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but I have more specific photos - just have 2900 images to edit - no time now.

in the jungle they were definitely in a shadier spot.

Probably some grow where they can't bloom. But some were blooming where it was shaded at 1 / 2 pm.

I think the weather there is relatively dry for tropical as there is always wind or strong breeze from the ocean. I saw no morning fog or dew.

What was most common was Myrmecophila tibicinis, Brassavola nodosa (these blooming in relative shade as well), Onc. cebolleta. Orchids in full sun seemed to suffer and be thirsty.
I wonder if terete leaves are about conserving water by reducing perspiration more than a response to light. Myrmecophilas seemed the ones to take sun best. But I have seen some that were too red. I just have to edit and organize all these photos.

But full sun there may be stronger than full sun on the 45th parallel

[Bud]

Beautiful blooms. The culture is quite a challenge for this. The regular Oncidium culture will not work for this...

[stefpix]

There is not much culture info on the web. wonder if needs 6 dry months in the winter ( I do not think it gets cold in the Yucatan peninsula where I saw it - lowest night was 67 F) and watered a lot in the summer when probably in active growth. It could be good for dry heated aoartments.

[euplusia]

Well, thousand and more kilometers away from the ever humid damp equatorial forests and closer to the tropics there are vast territories of open woodlands with periodically deciduous sclerophyllous shrubs and trees. Several names for this type of moister savannah come to my mind such as llano, cerrado, chaco. Today you'll find very often cattle farms there, the cattle looks like zebu. The biodiversity is immense.
Here the rhythm of life is water and no water. This is so predominant that for the ancient aztecs the lord of water (Tlaloc) and the lord of sun, light, fire and war (Huitzilopochtli) ruled the life.
The dry season is about five months and the season of heavy rainfalls lasts seven months, whereas for example in Rondonia the dry season is 40 - 50 days.
Years back I've seen hundreds of Onc. cebolletas on the thick lower horizontal branches of huge trees sheltered by a canopy of treetops in the countryside of Venezuela in a military camp. I've seen Brassavola nodosa growing on a candelaber cactus in full sunlight. In northern Argentina maybe hundred of Onc. jonesianum var. binotii grew on a dry wood with their short leaves upright, while the regular long leaves of onc. jonesianum could be found sheltered on a tree trunk facing downward.
We visited these areas in the dry season, and because of jet lag and a telephone call to Germany we once got up at 4 o'clock in the morning. I was surprised how chilling the night was and how wet the plants were of condensation of dew. Usually we were out at nine o'clock in the morning, and the morning sun had already dried the plants. Also when I wanted to take pictures of huge bulbs of catasetum macrocarpum in the foothills of the andes in Colombia, I realized that a very fine mist or spray affected the lens of my camera. But we never needed a windscreen wiper when driving. So the dry season is a time void of heavy rainfalls, but not bone dry.
Here at 49 degrees up north the situation in my greenhouse is as follows: In the months of summer I have shade cloth of 70 percent to reduce the heat of radiation on plant tissue, but the roof is covered with perspex to let UV light in. Only from the end of october to the end of february, when the sun barely reaches 17 degrees over horizon, I remove this and let all the light in. In the dry season from october to march I occasionally mist these plants in the morning of a sunny day. While in growth they get full water. But they are mounted with their leaves downward (Onc. cebolleta grows upright in nature), in order not to allow water to remain in the papery sheaths around the base of the terete leaves.
It is a very good idea to bring these succulent oncidiums into your home or appartment in winter. I agree that terete leaves are more important to reduce perspiration of water than to reduce striking sun.