San Diego County Orchid Society

Oncidium Alliance

A very large and diverse group of New World orchid genera with a wide distribution range and  very diverse habitats. The diversity makes it difficult to give generalized cultural information – it is necessary to have specific information on  climate conditions under which each species grows.

This group recently received several taxonomic revisions and former sections have now received genus status and species  have been moved between different genera.

All of the species share a similar flower morphology with many small flowers carried on a more or less long spike. Desite the small size of the individual flower, the large number on a spike makes them very showy and attractive to hobbyists. Also notable for this group are very thin and wiry roots for an epiphytic orchid. 

The habitats range from high elevation cloud forests (many of the Odontoglossums eg. Odontoglossum [Oncidium] crispum) to low elevation tropical rainforests to habitats with prolonged dry seasons (mule ear Oncidiums – now Trichocentrum – like Trichocentrum lanceanum or splendidum) and also specialized habitats of the twig-dwelling Tolumnia (formerly Equitant Oncidiums) species.

Luckily hybrids tend to be more adaptable and can be grown under a wider range of conditions. 

Below are links to AOS culture sheets which give more detailed information.