The Oncidium orchid is also known as the golden shower orchid, and in some areas people also refer to the Oncidium orchid as the Dancing Lady Orchid because the Oncidium orchid flowers resemble dancing ladies.
This is an extraordinarily large and diverse New World genus with an equally diverse number of habitats. Oncidium orchids occur naturally throughout the American Tropics from Florida to Argentina. This obviously makes cultural generalizations difficult. If you intend growing Oncidium orchids then it would be in your best interest to obtain more specific instructions from the grower who is distributing the Oncidium orchids. Some genera included are Aspasia orchids, Brassia orchids, Odontoglossum orchids, warm-growing Miltonia orchids (often called the Brazilian orchid type) and many of their hybrids. Hybridization of Oncidium orchids with Brassia orchids, Mitonia orchids and Odontoglossum orchids will result in an Oncidium orchid that has some warmth tolerance.
They are epiphytic, meaning they have pseudobulbs that store water and nutrients. The Oncidium orchid flower itself only comes in yellow with brown markings, however, the flowers of the Oncidium orchid hybrids come in most colors, and flower size is smaller than most orchids. On the upside, though, they have many, many flowers on each spike. These Oncidium hybrids often produce orchid flowers that last in excess of six weeks.
Temperatures for this group are generally considered intermediate to warm: 15 to 30° Celsius (59 - 86° Fahrenheit). Temperatures that are a little bit hotter are tolerated by the warmth tolerant Oncidium orchid hybrids if humidity and air movement are increased as the temperatures rise, a good general rule in any case.
Light needs can vary from bright to nearly full direct sun depending on the Oncidium orchid species and whether it is an Oncidium orchid hybrid that is cultivated as a warmth-tolerant orchid. Most Oncidium orchids will thrive with one to several hours of sun a day. Generally, thicker-leaved plants, such as Tolumnias also known as "mule-ear" and "equitant" oncidium orchids, can tolerate more light. If you cultivate your Oncidium orchids in a greenhouse then you are best advised to make use of a shade cloth which can be anywhere from 30 to 50 percent shade, depending on the orchid plants. If you cultivate Oncidium orchid in your home then the east, south or west windows are ideal. Many types of Oncidium orchids will even grow under artificial light. Take care however, since the Oncidium orchid that has been hybridized with the Odontoglossum orchid will require additional shading.
Most Oncidium orchids and the Oncidium orchid hybrids prefer open compost that holds moisture rather than water. Water requirements vary with the type of orchid plant. Generally, Oncidium orchid 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 two 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; many species have winter rest periods.
Humidity should be between 30 and 60 percent. Many Oncidium orchids require less humidity than other orchids. Most greenhouses have adequate humidity and the Oncidium orchid can easily be kept happy under those circumstances. If you grow your Oncidium orchids indoors then placing the orchid plants above moist pebbles in trays is ideal. If you happen to cultivate your Oncidium orchids in a shade house or garden outside, then they will require more frequent mistings to reduce the possibilities of dehydration. Dehydration of Oncidium orchids is usually manifested as crinkled leaves.
The Oncidium orchid is known to be a heavy feeder. The Oncidium orchid and its hybrids must be fed at half the recommended strength of most fertilizers once a week while the orchid plants are actively growing. A high nitrogenous fertilizer in spring will be beneficial in terms of new growth and a balanced fertilizer during the summer and the winter will keep your Oncidium orchid in peak condition. During autumn it is best to feed your Oncidium orchid with a high potash-based fertilizer to aid new flowering stems from the bulbs.
The Oncidium orchid species is relatively pest and disease free as fewer pests will attack them. On rare occasions you will find Oncidium orchids that have aphid infestation. This is usually those orchids that are placed in open shade houses.
Potting of Oncidium orchids should be done when new growth on the orchid plant is about one-half mature. This is usually in the spring. You can use fine-grade potting media with fine-rooted Oncidium orchid plants and coarser mixes with large-rooted orchid plants; the standard size is medium grade. Your Oncidium orchid should be positioned in the pot so that the newest growth is farthest away from the edge of the pot, thus allowing the maximum number of new growths before crowding the pot. Spread the roots of the orchid plant over a cone of potting medium and fill in around the roots. Firm the medium around the roots of the orchid plant with your fingers. Keep humidity high and the potting medium dry until new roots form.
The Tolumnias, or equitant and mule-ear oncidium orchids, as well as other fleshy-leaved or large-rooted orchid plants, can be grown on slabs of cork bark or tree fern or in pots filled with a coarse, well-drained medium such as charcoal, or even osmunda. This measure will facilitate the necessary drying between water applications required by these Oncidium orchids. These orchids detest wet feet.