The most easily available oncidiums, however, grow well under normal indoor conditions in the home as well warm conditions in the greenhouse. They have large pseudobulbs and a mass of thin white roots. The large leaves (up to 60cm/2ft) emerge from the pseudobulbs.
Oncidiums are more forgiving of bright, even direct, light than other popular orchids. They can cope with direct light in the morning and prefer bright or even very bright conditions. East, south or west facing windows are all suitable positions.
The leaves should be bright green as opposed to dark green or reddish green. Reddish green indicates too much light and dark green too little light.
During the growing season, water every few days, but allow the compost to become a little dry between waterings
In winter, reduce the watering to once a month or less. They can withstand considerable drought because their large pseudobulbs act as stores. Wrinkled pseudobulbs generally indicate a lack of water
Be careful not to overwater. Oncidiums have large, fleshy pseubobulbs and masses of roots; they are prone to rot. If you see a psuedobulb beginning to rot, cut it out with sterile secateurs and reduce the amount of water.