Oncidium orchids, often known as “Dancing Lady Orchids” due to their unique, skirt-like labellum, are a captivating group within the orchid family. Their popularity stems from their vibrant colors, intricate patterns, and prolific blooms that can last for weeks. The genus Oncidium encompasses a diverse array of species and hybrids, varying in size, shape, and growing requirements. This diversity means there is an Oncidium orchid suitable for almost any grower’s conditions.
Exploring Oncidium Diversity
The term “Oncidium” refers not only to the specific genus Oncidium but also broadly to a diverse group of related orchids within the “Oncidium Alliance.” This alliance includes closely related genera, such as Brassia, Miltonia, Odontoglossum, Tolumnia, and Rhynchostele. Breeders have extensively crossed these genera, creating numerous complex intergeneric hybrids with names like Colmanara, Beallara, Vuylstekeara, and Miltassia.
This genetic pool contributes to the wide range of characteristics observed across Oncidium types. The diversity includes variations in flower shapes, from star-like to highly ruffled, and a wide palette of colors, including yellows, browns, reds, purples, and green. These crosses also led to different growth habits, from compact plants suitable for windowsills to larger specimens with long, arching flower spikes.
Major Oncidium Groups
Oncidium orchids are categorized into several major groups, each with distinct characteristics and growing requirements.
The “Dancing Lady” type Oncidiums are the most recognizable, characterized by prominent pseudobulbs, which are swollen structures storing water and nutrients. These plants produce long, arching flower spikes with numerous small to medium-sized flowers, often in shades of yellow and brown with intricate patterns. They thrive in intermediate temperatures, with daytime temperatures ranging from 65°F to 80°F, and require bright, indirect light, similar to conditions under a dappled tree canopy.
Equitant Oncidiums, formerly classified under Tolumnia, are a unique group without pseudobulbs. Instead, they have small, fan-shaped, fleshy leaves that grow tightly together, resembling a miniature fan. Their flowers, though smaller than “Dancing Lady” types, are vibrant and produced on delicate, wiry spikes. These orchids prefer brighter light conditions, similar to Cattleya orchids, and warmer temperatures, between 70°F and 85°F during the day.
Mule-Ear Oncidiums are known for their thick, leathery, upright leaves that resemble a mule’s ear. Unlike “Dancing Lady” types, they have large, less prominent pseudobulbs often hidden by the leaf bases. These plants are robust and tolerant of drier conditions due to their succulent leaves. They prefer bright light, tolerating some direct morning sun, and intermediate to warm temperatures.
Intergeneric Hybrids combine characteristics from two or more genera within the Oncidium Alliance, resulting in a broader range of appearances and growing tolerances. For example, Odontocidium crosses combine the showy, cooler-growing Odontoglossum with Oncidium, resulting in larger, more complex flowers. Colmanara (a cross of Miltonia, Odontoglossum, and Oncidium) and Miltassia (a cross of Miltonia and Brassia) feature star-shaped or spider-like flowers with unique color combinations. These hybrids inherit a broader tolerance for various growing conditions, making them adaptable to typical home environments.
Popular Oncidium Varieties
Many Oncidium varieties are favorites among orchid enthusiasts for their beauty and straightforward cultivation.
Oncidium ‘Sharry Baby’ is widely recognized, known as the “Chocolate Orchid” for its fragrance resembling vanilla or chocolate. This “Dancing Lady” type hybrid produces long, branching spikes with numerous small, reddish-brown flowers and a white or pink lip. ‘Sharry Baby’ thrives in intermediate temperatures and bright, indirect light, making it suitable for many home environments.
Oncidium ‘Twinkle’ is a miniature hybrid known for its sprays of tiny, fragrant flowers. Available in white, pink, and red, ‘Twinkle’ plants remain compact, ideal for growers with limited space. This “Dancing Lady” type prefers intermediate temperatures and moderate light, blooming reliably in late autumn or winter.
Oncidium ‘Sweet Sugar’ is a popular “Dancing Lady” type, known for its vibrant yellow flowers resembling a cascade of golden bells. This robust hybrid produces multiple tall spikes, each bearing dozens of bright blooms. ‘Sweet Sugar’ is forgiving, preferring intermediate temperatures and bright, indirect light, and is known for consistent blooming.
Among intergeneric hybrids, Colmanara ‘Wildcat’ is a standout, recognized for its large, showy flowers with a combination of burgundy, yellow, and brown patterns. This hybrid, a cross involving Miltonia, Odontoglossum, and Oncidium, produces tall, erect spikes that can bear multiple blooms simultaneously. ‘Wildcat’ adapts well to intermediate temperatures and bright, indirect light, exhibiting the vigor found in complex hybrids.
Also notable is Beallara ‘Peggy Ruth Carpenter’ ‘Morning Glory’, featuring large, star-shaped flowers with mottled green and purple-brown petals and a prominent white lip. This hybrid, derived from Brassia, Miltonia, and Odontoglossum, produces fragrant blooms on tall spikes. ‘Peggy Ruth Carpenter’ prefers intermediate temperatures and bright, indirect light.
Cultivating Your Oncidium Variety
Successful cultivation of Oncidium orchids requires understanding their general needs and the specific requirements of different groups. Most “Dancing Lady” types and intergeneric hybrids prefer bright, indirect light, similar to an east-facing window or a shaded south-facing window. Equitant Oncidiums and Mule-Ear types require brighter conditions, tolerating some direct morning sun, which encourages more robust flowering.
Watering practices adapt to the Oncidium type and its water storage capabilities. “Dancing Lady” and Mule-Ear Oncidiums, with prominent pseudobulbs, tolerate drier conditions between waterings since pseudobulbs store moisture. Equitant Oncidiums, lacking pseudobulbs, require more consistent moisture and frequent watering, but still need good drainage to prevent root rot. Allowing the potting medium to approach dryness before rewatering is a good rule for most potted Oncidiums.
Temperature and humidity also play roles in Oncidium health. Many “Dancing Lady” types and intergeneric hybrids thrive in intermediate temperatures, with daytime temperatures between 65°F and 80°F and a nighttime drop of 10-15 degrees. Some Odontoglossum dominant hybrids may prefer cooler conditions, while Equitants and Mule-Ear types prefer warmer temperatures. Adequate humidity, between 50-70%, benefits all Oncidiums, provided by grouping plants or using a humidity tray.
Potting medium and repotting frequency depend on the plant’s growth habit and medium breakdown rate. Most Oncidiums prefer a well-draining, airy mix, such as fir bark, sphagnum moss, or a blend, allowing good air circulation around roots. Repotting is done every one to two years, or when the potting mix begins to decompose, after flowering when new growth begins. Equitant Oncidiums are grown mounted on cork bark or similar materials, reflecting their natural epiphytic habit and ensuring rapid drying between waterings.