Oncidium is a genus of about 370 species of orchid in the family Orchidaceae. It is distributed across tropical and subtropical America from Mexico, Central America and the West Indies to northern Argentina, with one species (O. ensatum) extending into Florida. Common names for plants in this genus include dancing-lady orchid.

A molecular phylogenetic study published in 2009 labeled the Oncidium alliance "grossly polyphyletic." In the same year, the American Orchid Society labeled the genus a "dumping ground". A consensus announced in April 2013 resulted in major taxonomic changes to Oncidium, Gomesa, Odontoglossum, Miltonia, and others. Much of this debate and subsequent housekeeping was initiated by significant research for the scientific publication Genera Orchidacearum Volume 5. One significant change is the move of most Brazilian Oncidium with a fused lateral sepal to the genus Gomesa. The inflorescences are borne in panicles, usually appear from the axils of recently matured growth and flower only once from the pseudobulb. The flowers are resupinate, the sepals and petals free from each other, egg-shaped to nearly circular, with a fiddle-shaped lip with a prominent warty fringe. The fruit is a capsule.

Taxonomy

The genus Oncidium was first described in 1800 by Olof Swartz in Kungliga Svenska Vetenskapsakademiens Handlingar (Proceedings of the Royal Swedish Academy of Sciences) The genus name Oncidium is derived from the Greek word ὀγκος, onkos, meaning 'swelling' and the diminutive -idium in reference to the prominent lip callus.

{| class="wikitable sortable"

|+ Nothogenera involving Oncidium

|-

! Nothogenus !! Parents

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|× Adacidium||Ada × Oncidium

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|× Adoncostele||Ada × Oncidium × Rhynchostele

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|× Aliceara||Brassia × Miltonia × Oncidium

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|× Arthurara||Brassia × Miltonia × Oncidium × Rhynchostele

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|× Aspacidopsis||Aspasia × Miltoniopsis × Oncidium

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|× Aspacidostele||Aspasia × Oncidium × Rhynchostele

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|× Aspasium||Aspasia × Oncidium

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|× Brapacidium||Aspasia × Brassia × Oncidium

|-

|× Brascidostele||Brassia × Oncidium × Rhynchostele

|-

|× Brassidiocentrum||Brassia × Oncidium × Trichocentrum

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|× Brassidium||Brassia × Oncidium

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|× Brassidomesa||Brassia × Gomesa × Oncidium

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|× Brassoncidopsis||Brassia × Miltoniopsis × Oncidium

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|× Crawshayara||Aspasia × Brassia × Miltonia × Oncidium

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|× Cuitlacidium||Cuitlauzina × Oncidium

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|× Cyrtocidistele||Cyrtochilum × Oncidium × Rhynchostele

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|× Cyrtocidium||Cyrtochilum × Oncidium

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|× Cyrtoncidopsis||Cyrtochilum × Miltoniopsis × Oncidium

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|× Dunningara||Aspasia × Miltonia × Oncidium

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|× Gomiltidium||Gomesa × Miltonia × Oncidium

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|× Gomonciada||Ada × Gomesa × Oncidium

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|× Gomoncidochilum||Cyrtochilum × Gomesa × Oncidium

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|× Howeara||Leochilus × Oncidium × Rodriguezia

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|× Lockcidium||Lockhartia × Oncidium

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|× Milenkocidium||Miltonia × Oncidium × Zelenkoa

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|× Milmilcidium||Miltonia × Miltoniopsis × Oncidium

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|× Milonzina||Cuitlauzina × Miltonia × Oncidium

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|× Miltadium||Ada × Miltonia × Oncidium

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|× Miltoncentrum||Miltonia × Oncidium × Trichocentrum

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|× Miltoncidostele||Miltonia × Oncidium × Rhynchostele

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|× Miltonidium||Miltonia × Oncidium

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|× Oncidesa||Gomesa × Oncidium

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|× Oncidettia||Comparettia × Oncidium

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|× Oncidopsis||Miltoniopsis × Oncidium

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|× Oncidpilia||Oncidium × Trichopilia

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|× Oncidumnia||Oncidium × Tolumnia

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|× Oncostele||Oncidium × Rhynchostele

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|× Oncostelopsis||Miltoniopsis × Oncidium × Rhynchostele

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|× Otorhynchocidium||Oncidium × Otoglossum × Rhynchostele

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|× Pettitara||Ada × Brassia × Oncidium

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|× Psychocidium||Oncidium × Psychopsis

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|× Reicheara||Aspasia × Miltonia × Miltoniopsis × Oncidium

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|× Rodricidium||Oncidium × Rodriguezia

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|× Scelodium||Oncidium × Scelochilus

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|× Schunkeara||Brassia × Miltonia × Miltoniopsis × Oncidium

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|× Trichocidium||Oncidium × Trichocentrum

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|× Warneara||Comparettia × Oncidium × Rodriguezia

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|× Zelencidiostele||Oncidium × Rhynchostele × Zelenkoa

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|× Zelencidopsis||Miltoniopsis × Oncidium × Zelenkoa

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|× Zelenkocidium||Oncidium × Zelenkoa

|}

Former nothogenera

Some nothogenera have been named based on hybrids involving Cochlioda or Odontoglossum, both accepted as synonyms of Oncidium ,

  • Harry Zelenko :The Pictorial Encyclopaedia of Oncidium (1997)
  • Koniger, W. 2003. New species of the genera Masdevallia, Oncidium and Sigmatostalix. Arcula no. 12: 298–311.