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Light: Bright to very bright
Oncidium orchids will develop to their full potential in bright light only, low light levels can lead to a non blooming orchid, or thin, short flower spikes with few blooms. An eastern window will suit its needs, while south and south west windows will also offer the light needed, but need to be partially shaded during hot summer sun to avoid leaf burns. A light green color of the pseudo bulbs and foliage will mean the orchid is receiving adequate light, while dark green will mean it isn’t receiving sufficient light.
Temperature: 60º F (16º C) to 85º F(30º C)
These orchids are very tolerant to high temperatures, provided they receive adequate hydration. The optimum temperature range however would be between 65º F (18º C) to 80º F(27º C). A difference between night time and day time temperatures will favor flower spike production.
Water: As the medium approaches dryness
Oncidium orchids don’t like to stay completely dry for long periods of time, although they can survive drought periods. Water thoroughly as the medium approaches dryness to avoid accordion shaped leaves and wrinkled pseudo bulbs. Lack of roots or improper hydration will lead to deformed leaves and flower spikes and even if they are very hardy orchids, keeping them evenly moist, but not soggy, will favor healthy growth and a nice appearance. Offering a more water retentive medium, but also good ventilation in the pot, will pay off in the long run. They can withstand slightly hard water, but very hard water can burn the fragile roots.
Oncidiums appreciate a humid environment, provided they receive good air movement to avoid disease. They can withstand dry air too, but will perform better in a 40% and above environment. Misting should only be performed in the morning, to let the orchid dry before night time and only in warm temperatures. When misting try not to place the orchid in direct sun to avoid leaf burns caused by the water droplets on the leaves.
Oncidiums are easy to keep by beginners as well, but they are sensitive to dehydration, which can lead to deformities of the leaves and flower spikes. If you cannot provide bright light, than re blooming this orchid can be tricky, if not impossible. A good feeding regime is also necessary for healthy growth, you can use either a balanced fertilizer (10-10-10), either a high nitrogen one, in the growing seasons. Additionally, a high phosphorus orchid food can be used as the flower spikes grow, to enhance blooms. Use half the strength recommended by the label if using tap water and never over fertilize, as Oncidium roots can be quite sensitive to salt built ups.
Many Oncidium hybrids have powerful fragrances, the most popular one being the Sharry Baby Oncidium, which can smell like chocolate and vanilla. They can produce 1 to 3 flower spikes per pseudo bulb, depending on the hybrid, which can branch out in optimum conditions.
The key factor in growing these orchids healthy, is a good understanding of their watering needs. Using a fine bark mix, or a coconut husk mix and offering good air ventilation in the pot, will greatly increase the chances of successful growing.