How to Bloom Oncidium Orchids

Keep these large orchids in 3- to 5-gallon pots to give them room to grow and to balance the long leaves and flower stalks. Plant in pots with holes in their bottoms to give the orchids good drainage. Oncidium orchids enjoy moisture but rot in standing water.

Grow these orchids in peat moss, wood chips or orchid potting medium. Oncidium orchids like moisture but don't thrive or bloom in inorganic potting media such as sand or gravel.

Give Oncidium orchids good light exposure year-round. Keep them in bright, indirect morning light and afternoon shade for best results. These orchids do well outdoors in the morning during the summer and require appropriate lighting for blooming. Don't put them outdoors during winter, as they require temperatures of more than 55 to 60 degrees Fahrenheit to survive.

Water Oncidium orchids once a week during their growth stages to keep them consistently moist. Pour water into the pot until it runs out the bottom The orchids won't grow flower stalks or bloom without proper water content. Restrict watering to every other week during dormancy periods.

Move the orchid into slightly cooler temperatures to encourage blooming. Nighttime temperatures of less than 65 Fahrenheit cue an Oncidium orchid to set flower stalks and buds. Leave the pot next to windows at night to achieve this temperature in fall and spring.

Feed Oncidium orchids with 1-1-1, 5-5-5 or 20-10-20 water-soluble fertilizer at one-fourth strength with every other watering to encourage blooming. Oncidium orchids require more nutrition during the blooming phase to grow and set flower stalks and buds. Reduce the feedings to every third watering during dormancy.