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Excerpts from Jim Conrad's
Naturalist Newsletter
notes from a camping trip in northern Guatemala's Petén department, April 1, 2019
DANCING-LADY ORCHID
Beside the highway cutting through El Rosario National Park on the east side of Sayaxché, Petén, northern Guatemala, an orchid had fallen to the ground from a tree at the forest's edge, as shown below:
The orchid's tangle of white roots are at the picture's bottom, center. The orchid's narrow, fleshy leaves radiate out from roots, and the flowering heads, or inflorescences, rise to the picture's top, right. One of the flowers appears below:
I lost a lot of time searching for an Oncidium species with flowers like this, because that's what I thought it was. Finally I learned that nowadays most experts have shifted our species from Oncidium, where it used to be, to the genus Trichocentrum, which at this time embraces about 68 species distributed from Mexico and Florida to Argentina. Of those 68 species a fair number occur in Guatemala. I can only make an educated guess aided by pictures on the Internet, that our plant is TRICHOCENTRUM ASCENDENS. All species in the genus sometimes are referred to as Dancing-lady Orchids.
Trichocentrum ascendens, occurrs in many habitats from swamps and mountain forests to trees in pastures and coffee plantations, throughout all of Central America, Colombia and the Caribbean area.
Leaves of orchids in the Oncidium/Trichocentrum complex arise from pseudobulbs, which in many species are very conspicuous water-storage appendages at the leaves' bases. In Trichocentrum ascendens the pseudobulbs are so reduced -- only about 1cm (1/3inch) long -- that they're hardly recognizable, and that's one of the species' field marks.
An unidentified expert on Wikipedia's Trichocentrum page writes that typical trichocentrum orchids are "...relatively small and squat with a short, few-to-several flowered inflorescence..." which contrasts sharply with the "...larger, heavier oncidiums with long, 'mule-ear' leaves and showy, branched inflorescences with many flowers, or the "rat-tail" species with terete leaves."