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Oncidium Alliance Culture

 Flower of Ons. Wildcat, an Oncidium intergeneric orchid with bolg burgundy patterns on a yellow background.

Oncidiums and their intergenerics are some of our all time favorites. Few genera can match the color, patterns, fragrance and easy of growth of these magnificent plants. There are few orchid alliances as a whole that are more suited to the beginner. And even fewer in which many of the available varieties have nearly identical culture. There are some exceptions (we're looking at you, Miltoniopsis) but they are generally the exception, not the rule. For this guide, I will refer to all Oncidium alliance plants as “Oncidiums.” At the end of this guide, I will list some common genera and nothogenera (hybrids across genera) that fall under the Oncidium umbrella. This is not an exhaustive list! There are many more genera and nothogenera, these are just some of the more common ones.

Temperature

Oncidiums are native to Central and South America. Specific regions are host to different species and even genera and may vary moderately in their local climate. However, these plants are adaptable and robust and can be grown in cool, intermediate and even warm conditions. Although they do best in intermediate temperatures, high 50s to low 60s as night and 70s during the day, these plants are high adaptable and robust. They will grow well and flower even if kept in the high 40s at night or up into the high 80s during the day. Culture will change slightly depending on your conditions. If they are kept on the cooler end of the spectrum, they should be allowed to dry out more between each watering to combat rot. If kept at the higher end of their temperature range, watering them more will help prevent heat stress and dehydration.

Light

Oncidiums grow and flower best when kept in moderately bright light. We call this the medium range, 1500 to 2500 foot candles. East and west facing windowsills are ideal as well as a partially shaded south facing window. It's important, especially in more southern climates or during summer, to protect plants from the midday, direct sun otherwise you may end up with significant sun burn on your plants. If plants are kept too shaded, they may grow well but rarely flower or produce few flowers per spike if they do. Their foliage is also usually a dark green. Slowly increasing the light of an otherwise healthy plant is usually enough to induce flowering on the next new growths. Alternatively, if your plant grows poorly and is a sickly yellow-green but still flowers, consider backing off on the light a bit. Oncidiums can be acclimated to nearly full sun but we have never found it to be in their best interests! Aim for light, green foliage, the color of crab grass or new tree leaves.

Potting

There are many different ways to pot Oncidiums and what you choose should be tailored to your conditions and personal gardening habits. Forgetful gardeners or those in hot and/or dry climates should consider a moisture retaining media and plastic or glazed pots. Those who are over attentive and like to fuss should consider faster draining media and/or clay pots or pots with aeration holes. For more information, please visit my potting guides. Click here for Part 1 and here for Part 2.

Water and Fertilizer

Oncidiums actively grow and flower year round with no discernible set schedule. As such, we water and fertilize year round. Other than adjustments for local climate, i.e. allowing plants to dry more in the colder winter, we water when plants are approaching dryness and fertilize regularly. Generally, fertilizer is applied three out of every four waterings at ½ the label strength (if using a houseplant fertilizer, cut that down to ¼). On the fourth watering, we use pure water to flush out built up fertilizer salts and waste and to promote root health. We recommend K-Lite or MSU orchid fertilizer formulas as they have been specifically formulated with epiphytic orchids in mind.


Common Oncidium Alliance Genera

  • Ada (Ada)

  • Brassia (Brs)

  • Cochlioda (Cda)

  • Comparettia (Comp)

  • Gomesa (Gom)

  • Ionopsis (Inps)

  • Miltonia (Milt)

  • Miltoniopsis* (Mps)

  • Oncidium (Onc)

  • Odontoglossum (Odm)

  • Psychopsis* (Pyp)

  • Rodriguezia (Rdza)

  • Rhynchostele (Rst)

  • Tolumnia* (Tolu)

Common Oncidium Alliance Nothogenera

  • Aliceara (Alcra) = Ada x Brs x Onc

  • Beallara (Bllra) = Odm x Brs x Cda x Milt

  • Brassidium (Brsdm) = Brs x Onc

  • Bratonia (Brat) = Brs x Milt

  • Columnara (Colm) = Milt x Odm x Onc

  • Degarmoara (Dgmra) = Brs x Odm x Milt

  • Miltonidium (Mtdm) = Milt x Onc

  • Odontioda (Oda) = Odm x Cda

  • Oncidopis (Oip) Mps x Onc

  • Oncostele (Ons) = Onc x Rst

  • Oncidesa (Oncna) = Onc x Gom

  • Ioncidium (I) = Inps x Onc

*Denotes different care requirements than standard care. Review plant's sale page for specific care recomendations.

**Names italicized and bolded are no longer recognized due to the merger of Odontoglossum and Cochlioda into Oncidium but are still utilized by many growers.