An Oncidium by Any Other Name Is Still a Delight to Grow and Flower

THE GENUS ONCIDIUM IS AMONG the largest in the orchid family. Various authors list the number of species anywhere from 300 to more than 600, depending on the taxonomic treatment. Name changes within the genus have occurred regularly in recent years, which is not surprising with such a large group.

As taxonomists grapple with the problems of sorting and making sense of this group, more than a few sections have been created that include but one genus. It will undoubtedly be some time before consensus is reached, in part because Oncidium is also closely related to several other genera in the Oncidium alliance with which it hybridizes, such as Odontoglossum, Miltonia and Brassia, to name just three.

Familiarly, oncidiums are known in the orchid world as dancing-lady orchids, a nickname given for the appearance of the flowers. To generalize in the extreme, oncidiums’ often yellow and brown blossoms are frequently small and occur in sizeable, branched sprays. Their most distinctive feature is usually a broad lip or labellum that dominates the flower and often resembles the full, flowing skirt of an animated dancer.

The dancing ladies belong to a remarkable and diverse group of orchids. We will take a brief look at nine types or examples.

As noted, the Oncidium species are a variable lot, and all are native to the tropical Americas, stretching from Florida through Mexico and Central America to Brazil and Argentina. They occupy a variety of habitats and grow in a wide range of elevations. Most species are epiphytic, although a few are terrestrial.

It is difficult to offer cultural guidelines for such a large group. Many thrive in intermediate to warm conditions. Some, from higher el-evations, need cooler situations. They can be grown potted or on mounts of cork or tree fern. Most have noticeably active periods of growth when they require ample water and nutrients, as well as dormant periods when watering should be withheld a bit.

A number of species can grow in a general collection. Many require good light to thrive and may become sizeable plants. I will never forget an Oncidium specimen that was brought to an orchid judging I attended a number of years ago. It sported clouds of flowers that reached for several feet in nearly every direction. The plant received a well-deserved cultural award, and perhaps the real marvel of it was that the exhibitor was motivated enough to devise a way to transport the mon-strous flowering plant to the event. As I remember, he had suspended it from the roof of a somewhat large panel truck and had driven cautiously. 

Many Oncidium species have been cultivated and perhaps each grower has a favorite. Some produce rather upright panicles of flowers, yet others are more arching. While yellow with mahogany patterning is the coloration most often associated with an oncidium blossom, you will find oncidium flowers sport-ing shades of pink, orange, white, burgundy and other colors.

A STARTING POINT  As a first example of a more or less typical species, Oncidium sphacelatum will suit as well as any. It is a rather vigorous grower with a native range from Mexico to El Salvador and Costa Rica. The branched inflor-escence may carry many 1-inch (2.5-cm) flowers that are bright yellow spotted red-brown. This would be a good choice if you want to produce a specimen plant in a short time. Each pseudobulb produces one or two narrow leaves that can reach 1–2 feet (30–60 cm) in length. The foliage is of the sort that in this genus is termed “soft,” i.e. not succulent or rigid.

MULE’S-EAR ONCIDIUMS   An-other type of dancing lady, Tricho-centrum (syn. Oncidium) caven-dishianum, produces a different foliage popularly called mule’s ear. This species can also become a large plant and carries a flower stem that may extend 3 to 6 feet (90–180 cm). It is unifoliate, having but one stiff, thickened leaf per pseudobulb. The fragrant, waxy, 2½-inch (6.25-cm) flowers are yellow to yellow-green with red to brown spots or blotches.

The mule’s-ear types grow well mounted on bark or planted in baskets. Because of their succulent foliage, they can withstand less water, but they do best with warmth, humidity and plenty of light.

COOLER GROWERS  While the petals and sepals are often of reduced size in many of the more familiar Oncidium species, there are plenty of examples with wider segments. These could make up yet a third type of Oncidium species that are often found at higher elevations, thus doing best under cooler growing conditions. Oncidium crispum, Oncidium praetextum (syn. enderianum) and Onc-idium gardneri are among them.

POPULAR HYBRIDS  As a fourth example, it is important to acknowledge the multitude of hybrids among the Oncidium species, those cheerful, primarily yellow sorts that are most frequently encountered. Many have wide, ruffled, yellow lips. Sprays of these blossoms create an effect unlike that of any other orchid and it is hard to imagine creating an orchid display without including at least one. A few of this sort include Oncidium Gower Ramsey (Goldiana × Guinea Gold), Oncidium Sweet Sugar (Aloha Iwanaga × varicosum) and Oncidium Aloha Iwanaga (Goldiana × Star Wars).

A FRAGRANT FAVORITE  Another Oncidium hybrid, Oncidium Sharry Baby (Jamie Sutton × Honolulu) probably deserves a solo spot on the dance floor. The hybrid was registered in 1983 and traces its roots to four species: Oncidium altissimum, Oncidium ornithorhynchum, Oncidium anthocrene (syn. powellii) and Oncidium leucochilum.

I have heard that the immensely popular hybrid has been mericloned in larger numbers than any other orchid. The flowers are primarily a dark shade many describe as burgundy. The lip is white to pale pink with purple splashes near the center and back edges. If it is the color that first catches your attention, it is the fragrance you will not forget.

Oncidium Sharry Baby has a scent that has been compared to that of chocolate. I am not certain that I concur, but have noted in my experience that the sense of smell seems to differ considerably between individuals. While some find this orchid’s perfume irresistible, others find it overpowering.

This grex is an example of a successful hybrid that was produced from comparatively ordinary parents. Oncidium Sharry Baby has garnered 10 AOS awards, yet neither parent has received one. The cultivar Onc. Sharry Baby ‘Sweet Fragrance’, AM/AOS, is most frequently encountered. One award was made to a mutation of Onc. Sharry Baby ‘Sweet Fragrance’, AM/AOS, about a decade ago, to a plant with variegated foliage. That plant, Onc. Sharry Baby ‘Pacific Paradise’, JC/AOS, verifies that genetic changes can and do occasionally occur with mericloned orchids.

TOLUMNIAS  If you desire the Oncidium-type flower but do not have room for large plants, the species and hybrids of the genus Tolumnia may be the answer. These are frequently called equitant oncidiums and were included in the genus Oncidium for many years. Equitant refers to the arrangement of the leaves, which are arranged fanlike in a single plane, similar to that of bearded iris.

There are about 20 species in the genus Tolumnia. They grow as small epiphytes and lithophytes and differ from oncidiums in lacking any but vestigal pseudobulbs. Most grow on twigs and some produce a somewhat tufted, stoloniferous habit. They range from southern Florida through the Caribbean.

The flowers of these plants are surprisingly large for the size of plant and are often borne on a long flower stem that extends well away from the foliage. The color range and pattern-ing available on Tolumnia hybrids 

is remarkable, ranging from dark burgundy and purple through fiery reds, yellows and oranges. Many of these trace their ancestry to the successful grex Tolumnia (syn. Oncidium) Golden Sunset (Stanley Smith × Tiny Tim) of a few decades back.

Culture of Tolumnia species and hybrids can be a bit tricky. While they benefit from regular watering, their root system demands excellent drainage and must not stay wet too long. They are perhaps best grown mounted or in small baskets and appreciate warmth and high humidity.

BUTTERFLY ORCHIDS  Another fascinating genus, closely related and previously included in Oncidium is Psychopsis, popularly known as the butterfly orchid. Four or five species occur in Central and South America. They have some of the most interestingly patterned foliage among orchids. It is reddish brown in color with spots and blotches of green.

But it is the flower and flowering habit of Psychopsis that is remarkable. The dorsal sepal and two petals are narrow and extended, resembling an insect’s antennae. The winglike lateral sepals are much wider; but it is the lip that is most prominent. Much like those of the smaller dancing ladies, it is full, round and ruffled. The flowers may reach 4 inches (10 cm) from top to bottom and are of typical oncidium coloration — yellow with red-brown bars, spots and blotches.

The most popular species, Psychop-sis (syn. Oncidium) papilio and Psychopsis (syn. Oncidium)  kramer-ianum, bloom successively from the same flower stalk for many months, usually producing one flower at a time. These thrive in good light and do best with high summer temperatures. For best results, keep them somewhat potbound in a freely draining mix, or try growing them mounted.

ROSSIOGLOSSUMS  The eighth dancing lady is more a tigress than a kitten, and is more closely related to the allied genus Trichocentrum than it is to Oncidium. Still, the genus Rossioglossum bears the coloration and patterning typical of many of its oncidium cousins, although it was previously classified as Odontoglossum.

The genus includes about six species of which Rossioglossum grande is perhaps the most notable. A well-grown flowering plant of this species is always a showstopper. The inflorescence carries four to eight waxy flowers that may each reach a 6-inch (15-cm) span. The sepals are yellow with bold red-brown barring; the petals are typically bright yellow, red-brown at the lower half. The lip is pale yellow or whitish, sometimes flecked with brown.

Rossioglossum grande thrives in a rather dense growing medium that might contain a bit of sphagnum moss for moisture retention. Intermediate conditions and bright light are recommended. Water generously when in active growth but restrict water when dormant. Flower spikes develop in late summer to autumn.

INTERGENERICS  Finally, it seems important to mention at least one from the abundance of Oncidium alliance hybrids popularly grown today, and Colmanara Wildcat will get the nod. The grex is the result of crossing Odontonia Rustic Bridge and Odontocidium Crowborough. It was registered in 1992 and has thus far accumulated more than 60 AOS awards.

Colmanara Wildcat, which is now placed in the genus Odontocidium, traces half of its lineage to two Oncidium species, Oncidium fuscatum (syn. Miltonia warszewiczii) and Oncidium leucochilum. The award winners of Colmanara Wildcat gen-erally have flat, waxy flowers. Coloration varies from yellow with subtle mahogany markings to burgundy and other nearly solid colors, including some with rich patterns. Indeed, there are so many examples that a favorite is hard to choose.

If none of the Colm. Wildcat cultivars catches your fancy, look to other intergeneric crosses such as Brassidium (Brassia × Oncidium), Withnerara (Aspasia × Miltonia × Odontoglossum × Oncidium), Wilsonara (Cochlioda × Odontoglossum × Oncidium) and Burrageara (Cochlioda × Miltonia × Odontoglossum × Oncidium), and others. Among them you are sure to find ladies that, far from being wallflowers, are ready for the dance.