Oncidium

Light needs can vary from bright to nearly direct sun, depending on the species. Most will thrive with 1-5 hours of sun a day. Generally, thicker-leaved plants, such as "mule-ear" and "equitant" types can stand more light. The more light will typically give you more blooms.

• In a greenhouse, shade to part-sun, or about 21,500-64,500 lumens (2,000-6,000 foot-candles), depending on the plants.
• In the home, east, south, or west windows where they will get about 1-5 hours of sun are ideal.
• Many types of Oncidium will grow well under artificial light. Use lightbulbs/LEDs of your choice that are about 1-2 feet above the plant and emit >10,000 lumens (900 foot-candles). The lowest amount of lumens for growth is about 2,000 lumens (100 foot-candles), though flowering may be poor.

Temperature tolerance for this group is generally considered intermediate to warm: 55F-60F (13C-16C) at night, and 80F-85F (27C-29C) during the day. They are happy indoors at room temperature, and you can be successful even if the temperature does not swing that much from day to night. A good general rule: temperatures up to 95F-100F (35C-38C) are tolerated, but only if the plant cools down to 70F-80F (21C-27C) at night and water is increased.

Requirement vary with the type of plants. Generally plants with large fleshy roots or leaves need less-frequent watering than thin-leaved or thin-rooted plants. Watering should be through and the medium should dry at least halfway through the pot before watering again.

If insufficient water is given or if there is too much time between waterings, the plants will exhibit “accordion” growth. Avoid wetting foliage, as they are rather susceptible to various infections. The frequency of watering will depend on how fast it takes for the media to dry in your conditions.

• In a greenhouse, you should water at least daily regardless of whether it is potted or mounted. Water twice a day if the temperatures are above 85F (29C) regardless of whether or not it is potted or mounted.
• Indoors – These should only be grown potted, and you should keep the media perpetually lightly moist like a wrung-out sponge. The frequency will depend on how fast it takes for the media to dry in your conditions.

Humidity should be between 30 to 60 percent. many Oncidiums require less humidity than other orchids. In the home, placing the plant above moist pebbles in a try is ideal. Be sure to incorporate airflow if conditions are soggy, or the humidity is >75%.

Fertilize regularly to produce strong pseudobulbs. For potted plants in bark-based media, use regular strength to ½ strength of a high nitrogen formulation (such as 30-10-10) while plants are in active growth. A 20-20-20 formulation should be used on plants in other media or on slabs. A bloom-booster formulation (such as 10-30-20) should be used as flower spikes are forming. Do not fertilize during the winter.

Potting should be timed to coincide with the initiation of new growth, usually in the spring. However, these plants can grow year-round, so anytime is the right time, as long as they are not in spike. New roots will be produced quickly at the time of new growth, and plants will experience minimal setbacks. These plants have vigorous root systems and require an evenly moist, but breathable potting medium during the growing season. Even though they can be mounted, many greenhouse growers pot their Oncidium to ensure that they don’t dry out. When repotting, you should position the newest growth away from the edge of the pot, allowing the maximum number of new growths to form in the center as the plant expands. Spread the roots over a cone of potting medium and fill in around the roots. Firm the medium around the roots.

• In greenhouses, plant in anything from 100% sphagnum to 50% sphagnum and 50% fine-grade orchid bark mix. Planting in 100% treefern fiber (or mixed with some sphagnum) also works.
• Indoors, plant in either 100% tree fern fiber or 1/3 sphagnum and 2/3 fine orchid bark mix or tree fern fiber (or both). Planting in 100% sphagnum also works, as long as it is not sitting in water.

Equitant, or twig epiphytes, and mule-ear, more succulent types, as well as other fleshy-leaved or large-rooted plants can be grown on either mounts of cork bark or tree fern or in pots filled with a coarse, well-drained medium. This allows the drying between waterings that these types need. Keep in mind that equitant types need either very quick wet/dry cycles (going from wet to dry in a few hours, then wet to dry again in one day), or high humidity and normal watering cycles. Oncidium are especially easy to bloom, because they have no blooming requirements. Many species and hybrids will simply bloom once a new growth matures, which can happen as often as 3x a year!

Further information can be found on the Oncidium genus page.

Best orchid care practices are also provided for watering, repotting, and fertilizer types. There are also detailed discussions of growing orchids indoors, outdoors, or in greenhouses.

For more information on genus name changes, see Taxonomy.