This is an extraordinarily large and diverse alliance with an equally diverse number of habitats. Oncidiinae may originate anywhere from sea level in the tropics to the high elevations of the Andes. This obviously makes cultural generalisations difficult. More specific instructions may be available from other sources. Some genera included are Brassia, Miltonia, Miltoniopsis, Oncidium, Gomesa, Tolumnia, Psychopsis, Trichocentrum, Zelenkoa and more.
Temperature for this group is generally considered intermediate to warm: 14℃ at night and about 30℃ during the day. Temperatures up to 38℃ are tolerated if humidity and air movement are increased as the temperatures rise, a good general rule in any case.
Needs can vary from bright to nearly full direct sun depending on the species. Most will thrive with one to several hours of bright light per day. Generally, thicker leaved plants, such as Tolumnia and Trichocentrum benefit from more light. In a greenhouse, 20 to 60 percent shade is required depending on the plants.
Requirements vary with the type of plant. Humidity should be maintained at about 40%. Generally, plants with large fleshy roots or leaves need less-frequent watering than thin-leaved or thin-rooted plants. Watering should be thorough, and the medium should dry at least halfway through the pot before watering again. This may be every 2 to 10 days depending on weather, pot size and material, type of orchid and type of potting medium. Plants not actively growing should be watered less since many species have winter rest periods. Fertilise regularly while plants are actively growing. Applications of 30-10-10 formulations twice a month are ideal for plants in a bark-based potting medium.
Should be done when new growth is about half mature, which is usually in the spring. Fine-grade potting media are usually used with fine-rooted plants and coarser mixes with large-rooted plants. Tolumnia and Trichocentrum, as well as other fleshy-leaved or large-rooted plants, can be grown on slabs of cork bark or tree fern or in pots filled with a coarse well-drained medium allowing drying between waterings that these types need.