Cultural Notes for Odontoglossum / Oncidium / Brassia Alliance

The Odontoglossum/Oncidium Alliance is becoming very popular both for ease of growing and long-lasting sprays of flowers. They can be grown in the home, on a stoep, as well as in a sheltered area in the garden or in the greenhouse. Oncidium types will bloom once a year, although some Odontoglossums have been known to bloom two or three times a year. All combinations of “Odonts” and Oncidiums and related types have been produced through hybridising and offer a wide range of colour patterns as well as cultural flexibility.


Most Odontoglossums and their hybrids prefer filtered, subdued light and enjoy to grow cool. The Oncidiums prefer bright light, much the same as you would give a Cattleya. The leaves should be bright green as opposed to dark green or reddish green. Reddish green indicates too much light and dark green indicates not enough light.


Odontoglossums must be kept continuously moist (but not soggy and water logged) below the surface of the potting media. Ondiciums should become moderately dry between waterings, as do Cattleyas. Generally they require more water while the new shoot is growing and less once the bulb has formed. Fertilize your plants at least twice a month. We recommend a hydroponic feed, such as Starke Ayres Nutrifeed, throughout the growing season. This can occasionally be alternated with an organic fertilizer.


Odonts/Oncidiums enjoy moist air, requiring a minimum of 40-50% humidity in the immediate vicinity of the plant. Humidity should be increased with higher temperatures. The ideal humidity is between 55 and 75%, with as much ventilation or air movement as possible without any cold drafts. Morning misting of foliage is also helpful, especially during periods of hot weather.


Equitant oncidiums should be mounted on rough bark such as cork oak. Mist well daily and fertilize at least once a week during the growing months. They bloom spring-time through to summer.


Most Oncidiums and their hybrids are intermediate in their temperature preferences. Odontoglossums tend to prefer cool temperatures.


Repot Odontoglossums and Oncidiums at least every two years. As a general rule, repot them when the new shoot is 5 to 6 cm tall, or when new roots appear. All the old mix should be shaken off the roots and any dead roots should be removed. If dividing, keep the divisions in clumps of three to five bulbs. Medium to fine bark is preferred. The base of the new growth should be potted about 1 cm (no deeper), into fresh bark, then resume normal watering. Use Outeniqua Orchids Seedling mix for this group. For plants in pots of 15cm and greater, Outeniqua Orchids Cattleya Mix can be used.