Oncidium Intergeneric hybrid Orchids
These are characterized by the long, grass-like foliage that meet at bulbous stems and have a variety of different flower colors and shapes that most often bloom in a spray.
Moderate-bright light is best (2000 footcandle – 2700 footcandle), often equivalent to a bright East or West facing window, or in winter a South-facing window. Window size also affects the amount of light : bigger than a standard picture window (24”x 36”) means more light, smaller means less light, so a 10’wide, floor-to-ceiling North window can be sufficient, as well as a small South facing window. Too little light can result in shorter stems or fewer, smaller flowers, but too intense light can cause sun burn and scarring if strong light sits on the leaves for an extended period of time. This is usually a concern in the summer mid-day direct sun, but not early morning or late afternoon sun.
Most Oncidiums and their hybrids prefer intermediate temperatures to grow and flower. A range of 65 - 85 F is ideal for flowering and growing. If the temperature is above 90 F for extended periods, reduce light to prevent overheating, and make sure that the potting mix is on the drier side, since heat waves are often accompanied by droughts in their native climates. Many Intergeneric hybrids do well in cooler conditions down to 55 F, especially during flower development stages, resulting in darker, heavier flowers, as well as making the flowers last longer.
Water and Fertilizer
Although they are capable of withstanding an extreme drought, inadequate watering will result in shriveled pseudobulbs. For best growing and flowering, somewhat regular water and fertilizer are important. Generally, water when the potting mix is dry to the touch, but still has a little humidity (like a wrung-out sponge) but not yet bone dry; one saying is to water the day before it dries out. If the roots stay wet consistently, then they can get infected and rot, like a sponge that stays wet all week compared to one you let dry out regularly. It’s easier to err on the side of staying dry, but if the medium gets fully dried out, then it takes more effort to wet again, by either watering several times by waiting 30 minutes between each watering or soaking for up to 12 hours, and not watering until the potting medium is nearly dry again.
Fertilizer is best done with a weak solution, about ¼ – ½ teaspoon of soluble fertilizer (when starting with something like an all purpose 20-20-20 fertilizer) and use when actively growing or about every two months, allowing the excess to freely drain through.
Cut the flower stems to the base after the flowers fall off; the next flowers come from new shoots at the base of the plant and take approximately 6 months to a year to rebloom.