Oncidiums are popular indoor and florist orchids for a very good reason, their large drooping clusters of dozens of flowers. They have been bred freely.
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Light
Oncidiums are much more tolerant of bright or direct light than other common orchids. Oncidiums can handle direct light in the morning and even prefer brighter conditions that are very bright. They tend to enjoy light just like the fancy dendrobium orchids.
Drinking water
During the growing season, water daily or every other day. Be careful, though, as drainage is an absolute priority. The potting medium must be completely non-draining. Plants can also be grown on slabs or in baskets. If you see the pseudobulb starting to rot, cut it off with sterile pruners and reduce the amount of water. In winter, reduce watering to every two months or less. They can withstand considerable drought because of their large pseudobulbs. Wrinkled pseudobulbs are generally a sign of dehydration.
Fertilizer
Throughout the growing season, apply a weak orchid fertilizer every two months or spread slow-release pellets into the potting medium early in the season. Although there are many species, in general, the larger the tree, the more food is available.
Temperature
Oncidiums can be found in a variety of habitats, from semi-arid subtropical lowlands to cool, cloudy forests. In general, the most common types of magnolia, which have small yellow flowers, large pseudobulbs, and banded leaves, are intermediate species to warm-loving orchids. Do not expose them to cold winds or temperatures below 50 F. Even temperatures in the mid-50s will slow growth with prolonged exposure.
Bloom
Oncidiums are in beautiful bloom. A large, well-developed tree can produce yellow flowers of six or seven branches. The effect is very much like a butter cloud. The most common species include O. leucochilum, O. longipes, O. ironic, O. pulchellum, as well as many hybrids. Although oncidium are known for their yellow flowers, other varieties are still available. O. Sharry Baby is sometimes called the chocolate orchid because of its brown flowers with a strong cocoa smell.
Gourd and repotted
Oncidiums prefer to be grown slightly underserved in a substrate made of very draining bark. Many oncidium will form large clusters of pseudobulbs and grow into rather large trees. They can be easily divided into clumps when repotting. Just make sure you have at least three pseudobulbs in each division. In general, only repot when necessary.