Grow Oncidium Twinkle orchids in a small planter filled with potting mix formulated for orchids. Repot the orchid annually in spring. Replace the old orchid soil with a fresh batch. Use a pot designed for orchids, with vertical side drainage holes, for the soil to dry quickly.
Place the pot in a tray filled with pebbles and water to keep the environment humid. If your climate is very dry year-round, such as the Southwest desert, keep a humidifier running in the same room as the orchid.
Provide indirect bright to medium light. An Oncidium tolerates some direct morning sun, but it needs shielding from afternoon rays. Place it by a window with sheer curtains, for example. If the temperature allows, move the pot outdoors in the morning and take it back inside in midday.
Control the environment's temperature, keeping it between 68 and 80 degrees Fahrenheit during the orchid's active growing season. Drop the thermostat to 55 to 65 degrees Fahrenheit in winter.
Irrigate Oncidium Twinkle until excess water flows out of the drainage holes. Hydrate the plant again in the same manner whenever the soil dries to a depth of 1 inch. Increase irrigation frequency if the plant shrivels.
Feed the plant an orchid fertilizer every other week while it is actively growing. Increase the feeding interval to monthly in winter. Apply the fertilizer according to the rates listed on the label of the brand you selected.