Oncidium onustum is endemic to the north of South-America, where it can be found at altitudes ranging from 25 to 1200 m. These are regions with long, arid winters. The orchid's flowers from summer till fall. Countless yellow flowers appear with a size reaching up to 2 cm. At the stem Oncidium onustum has 'reservoirs' of about 2,5 cm for storage of water and nutrients. From this reservoir one single thick leaf appears. The orchid grows in trees, where it lives in the shadow of neighboring plants

In nature Oncidium onustum mostly grows at moderate altitude. Therefore, warm night temperatures of about 19-29 degrees Celsius are preferable, and even a bit higher during the day. The orchid needs plenty of water during the flowering period, preferably combined with orchid nutrition. After the blooming no more watering is required. Only as the new stalks appear, one can slowly start to water the orchid again. Oncidium onustum grows optimally with high humidity. To achieve this place other plants and sphagnum (a type of moss) in the proximity of the orchid, or spray the leafs with water in the morning.