Oncidiums are popular indoor orchids for a very good reason—their large sprays of flowers often sag with dozens of blooms. One common name for these orchids—dancing lady—is assigned because of the highly modified ruffled flowers.There are actually several hundred recognized Oncidium species, but the naming is not stable, so there is considerable flux as experts reclassify plants. They are readily hybridized, so new varieties are regularly introduced. The most common oncidium orchids grow well under normal indoor conditions. They have large pseudobulbs (a bulbous thickened area of the stem) that come up from a mass of thin white roots. The large leaves can get up to 2 feet long and emerge from the pseudobulbs. Oncidiums typically flower in the fall.
|Common Name||Oncidium orchid, onc. orchid, dancing-lady orchid|
|Botanical Name||Oncidium spp.|
|Mature Size||1.5-10 ft. tall, 1-2 ft. wide|
|Flower Color||Yellow, pink, red, green, purple|
|Hardiness Zones||9–12 (USDA)|
|Native Area||Central America, South America, Caribbean|
Oncidium Orchid Care
Oncidium orchids are by nature epiphytic plants that dwell on tree bark rather than in soil, and they favor more sunlight than other orchid genera. Placing them in an east, west, or south-facing window lined with a sheer curtain provides an appropriate amount of light.
Oncidiums are much more forgiving of bright or direct light than other popular orchids, especially the Phalaenopsis. Oncidiums can handle direct morning light and even prefer bright to very bright conditions. They tend to enjoy the same light that Dendrobium species orchids prefer.
Oncidium orchids are epiphytic plants that do not grow in traditional soil or potting mix at all, but rather they are normally potted in a bark-based potting medium. This medium is typically sold as orchid mix, and has very good drainage.
Various Oncidium species differ somewhat in their water needs, but in general, most need to be watered every two to ten days during the growing season. Those with thicker leaves and roots can be watered less frequently than those with thin leaves. Use lukewarm or room-temperature water when the growing medium is half-dry.
Be careful, though, because drainage is an absolute priority. The potting media must be perfectly free draining.
Temperature and Humidity
Oncidiums can be found in many habitats, from semiarid subtropical lowlands to cool and misty cloud forests. The ideal growing environment is 55 to 60 degrees Fahrenheit at night, and 80 to 85 degrees during the day. Temperatures up to 95 to 100 degrees can be tolerated if these high temps are matched by increased humidity and air circulations.
Humidity levels should be kept between 30 and 60 percent. It can be difficult to maintain proper humidity in regions with cold, dry winter air, so using a room humidifier—or placing the pot on a shallow water-filled dish filled with pebbles is recommended.
During the growing season, feed with a weak orchid fertilizer bimonthly or scatter slow-release pellets in the growing media at the beginning of the season. A 30-10-10 formulation is a good choice for bark-based potting mix; for woods slabs, use a 20-20-20 formulation. Although there are many species, in general, the larger the plant, the more heavily it will feed.
Types of Oncidium Orchids
There are literally hundreds of oncidium orchids available. The most popular species include:
- Oncidium leucochilum
- O. longipes
- O. sarcodes
- O. pulchellum
There are also many hybrids available, crosses between two Oncidium species. Although oncidiums are known for their yellow flowers, other varieties are available. Oncidium 'Sharry Baby' is sometimes called the chocolate orchid for its sprays of brownish flowers with a rich cocoa scent.
When your orchid stops blooming, wait for the flowers to fall off naturally and allow the stem to die entirely before cutting it back. Pruned orchids may generate a second flower stalk, though once-a-year blooms are common.
Propagating Oncidium Orchids
Many oncidiums will form large clumps of pseudobulbs and develop into rather large plants. They can be easily divided into clumps when repotting. Just make sure you have at least three pseudobulbs in each division. Here's how to do it:
- Carefully remove the plant from its pot and divide it to sections, each containing at least three pseudobulbs.
- Replant each into its own pot filled with bark-based growing medium.
- Planted divisions should be sprayed, but not watered, until new root growth is obvious. At this point, they can be watered in the same way as established plants.
How to Grow Oncidium Orchids From Seed
Propagation of orchids by seed is a tricky operation that is usually practiced only by professionals or very serious amateurs. It requires special materials and carefully controlled conditions. In nature, seeds germinate only through a complex interaction with a mycorrhizal soil fungi, and achieving artificial germination requires laboratory-like conditions. Few amateurs are willing to spend months getting seeds to sprout and sometimes years to nurture the seedlings into flowering plants, when vegetative propagation by simple division is relatively easy.
Potting and Repotting Oncidium Orchids
Oncidiums like to be slightly underpotted in a very free-draining bark-based potting media. In general, only repot when necessary. An orchid will often thrive happily for several years before it becomes so root-bound that division and repotting is necessary.
In the winter, reduce watering to bimonthly or less. Oncidium orchids can withstand considerable drought because of their large pseudobulbs. Wrinkled pseudobulbs generally indicate a lack of water.
Common Pests & Plant Diseases
Because oncidiums have large, fleshy pseudobulbs and masses of roots, they are prone to rot. If you see a pseudobulb beginning to rot, cut it out with sterile snippers.
Oncidium orchids are prone to many of the same pests that affect many houseplants, including aphids, mealybugs, scales, two-spotted spider mites, and thrips. These insects can be treated with the same insecticides used for other plants, including horticultural oils and synthetic pesticides, such as malathion. Good hygiene—keeping affected leaves pruned and plant debris removed—will minimize pest problems.
How to Get Oncidium Orchids to Bloom
Oncidiums are magnificent in bloom. A large, well-grown plant might yield six or seven-branched sprays of yellow flowers over a period of several months, often beginning in late summer. The effect is very much like a cloud of buttery butterflies. But orchids are often purchased while they are already in bloom, and it's often a disappointment when the orchid fails to rebloom after the spectacular initial display.
Getting your orchid to reliably rebloom is a matter of providing it with the right conditions:
- Oncidiums need a good amount of light to rebloom. Remember that this type of orchid needs more light than most other orchid genera—though not direct sunlight.
- After the bloom period has concluded, prune back the flower stem, which will stimulate reblooming.
- Most importantly, the orchid need temperature conditions that simulate a natural environment, meaning nighttime temperatures that fall to 55 to 60 degrees Fahrenheit, but warmer temperatures during the day. Without cool nights, these orchids will be shy about reblooming.
With careful control of conditions, it's possible to get your oncidium to rebloom two or even three times a year, with blooms present nearly year-round.
Common Problems With Oncidium Orchids
Orchids can be notoriously fickle, but oncidiums are often one of the easier orchids to grow, once you get the growing conditions mastered. But watch for these issues:
The most common issue, other than failure to rebloom (see above) is discolored leaves, which is usually the result of improper light. An oncidium orchid getting the right amount of light will have light, yellow-green leaves. If the leaves are dark green, it is likely not getting enough light, and too much light can make the leaves red-tinted.
Dark Spots on Leaves
Dark spots on leaves is usually the result of a bacterial infection, but it is rarely very serious. Improving air circulation in the room will usually cause the infection to vanish.
Browned Leaf Tips
When the leaf tips on an orchid turn brown, it is usually a sign of chemical burn caused by excessive fertilization. Give the plant extra water to flush the salts from the soil.
Can I grow oncidium orchids outdoors?
In regions that are frost-free, potted orchids can make good patio plants. But it is important to shield them from cold temperatures by bringing them indoors when temps fall to 50 degrees Fahrenheit or below.
How long does an oncidium orchid live?
An oncidium orchid can thrive for many decades if it is is divided and repotted every few years—and if it has ideal growing conditions.
Are there any oncidium orchids that are notably fragrant?
'Sharry Baby' has a distinct chocolate aroma. 'Twinkle' has a vanilla-like smell. Another popular fragrant orchid is the miniature Oncidium cheirophorum. If you enjoy the smell of citrus, try Oncidium chrysomorphum.
Care of Ondidium. Smithsonian Gardens.
Oncidium Culture Sheet. American Orchid Society
How Are Orchids Propagated? The American Orchid Society.
How to Grow Orchids From Seeds. Orchid Bliss.
Cating, R. A., and A. J. Palmateer. Bacterial Soft Rot of Oncidium Orchids Caused by a Dickeya Sp. (Pectobacterium Chrysanthemi) in Florida. Plant Disease, vol. 95, no. 1, 2011, pp. 74–74., doi:10.1094/pdis-07-10-0523
Orchid Pests and Their Management. University of Illinois Extension.