South & Central America / Mexico
Oncidiums are a delight to grow especially for those who have limited space. They can bloom several times a year and can also bloom with multiple spikes off a single pseudobulb. The flowers of the Oncidium genus come in shades of yellow, red, white and pink. The petals are often ruffled on the edges, as is the lip. The lip is enormous, partially blocking the small petals and sepals.
Most Oncidium and their hybrids prefer filtered, subdued light. The Oncidiums prefer bright light.The leaves should be bright green as opposed to dark green or reddish green. Reddish green indicates too much light; dark green indicates not enough light.
Oncidiums enjoy moist air, requiring a minimum of 40-50% humidity in the immediate vicinity of the plant. Humidity can be increased around the plant by placing the pot on an inverted saucer in a baking pan filled with pebbles, rock chips, etc., and water. Keep water level below top of pebbles so that the plant will not have "wet feet" from setting in water. Morning misting of foliage is also helpful, especially during periods of hot weather.
Potting & Media
Grow these orchids in small deep pots to accommodate the large furry root system. You can pot them in bark, perlite, charcoal along with sphagnum moss to retain moisture. Alternatively, you can substitute bark with coconut husk chips as they do not break down as quickly. Just be sure to wash coconut husk chips very well to get rid of any remaining salt before potting. Salt will burn orchids’ roots.
Any balanced orchid fertilizer (look at the numbers on the container, 20-20-20, etc.) can be used to fertilize your orchid. Weakly (¼ strength), weekly works well. Once a month use clear water to flush any accumulated salts from the potting mix.