Oncidium (on-SID-ee-um), or Dancing Lady Orchids are more difficult to grow than Phalaenopsis, Paphiopedilum or Cattleya orchids, but their abundant sprays of yellow flowers make them worth the effort . Oncidiums are becoming increasingly popular as new and easy-togrow hybrids are developed. Some of the new hybrids include Oncidium Grower Ramsey, Oncidium Sweet Sugar and Oncidium Taka. The genus Oncidium includes about 600 species of epiphytic plants that are native to the New World Tropics.
Oncidiums are high-light orchids, requiring more than 2500 foot candles. Most Oncidiums perform best with one to several hours of sunlight daily, but plants with thick leaves can tolerate more light than those with thinner leaves. A bright south-facing window is ideal for these plants. To grow Oncidiums under artificial light, place four 40-watt fluorescent tubes supplemented with incandescent lights 6-12 inches above the plant. Metal halide and sodium-vapor bulbs can also be used, but they should be placed farther away from the plant. They prefer daytime temperatures in the 80s. Nighttime winter temperatures should be a minimum of 55F. Oncidiums require less humidity than many other orchids, ranging from 30 to 60 percent. Humidity levels in the home can be increased by placing the plants on waterfilled trays of gravel, or by placing a humidifier near the plant. Plants with thick, fleshy leaves need less frequent watering than those with thin leaves.
All Oncidiums should be allowed to dry between watering. Thick-leaved Oncidiums can be grown on slabs of cork bark or tree fern, or in pots filled with course materials such as charcoal. Oncidiums in a bark-based potting medium should be fertilized twice a month with a onequarter strength diluted 30- 10-10 fertilizer. For plants in other growing media, fertilize with a 20-20-20 fertilizer. Repot Oncidiums in the spring or when new growth is onehalf mature.