How to Grow: Oncidium Orchid Care
Updated: May 5
The Oncidium family is very large and includes many flower varieties. The most common flower variety is often referred to as the "Dancing Lady". Oncidiums are popular indoor and florist orchids for a very good reason, their large sprays of flowers often sag with dozens of blooms. They have been freely hybridized. There are actually several hundred recognized oncidium species, but the naming is not stable, so there is considerable flux as experts reclassify plants.
Oncidium orchids are among the most diverse orchids in the world. One of the most famous cultivars is Oncidium kramerianum, originally from Colombia and Ecuador. This one is called the “butterfly orchid” because of its golden-yellow flowers with brown freckles. Another popular cultivar is Oncidium known as “Sharry Baby.” Oncidiums may originate anywhere from sea level in the tropics to the high elevations of the Andes. This makes cultural generalizations hard. So it is prime to know the Natural Habitat of your Oncidium.
They are often described as temperamental and difficult to grow. However, with proper care, it’s possible to grow them relatively easily. It’s important to know what to do and what NOT to do in order to successfully grow these beautiful orchids. This instruction sheet deals with Oncidium types that have thin leaves, pseudobulbs, and branching sprays of bloom.
Oncidium orchids are specific when it comes to light requirements. It depends on their growth stage as well as the time of day and season. When they are first starting to grow and blossom, they need direct sunlight for several hours per day. Once they start to blossom and give flowers, it’s important to move your orchid to a cooler place without direct sunlight. Too much direct sunlight can actually burn blossoms. Generally speaking, it’s best to keep your orchid in a semi-shady to semi-sunny environment.
At home, east or west windows are ideal. South windows will work but one should be careful of the brilliant sun that will come in during the fall through spring months. If you have miniblinds or sheer curtains, you can break the light so that it is more diffused. Many types of oncidiums will grow under artificial light, Four fluorescent tubes supplemented with incandescent bulbs and placed 6 to 12 inches over the plants are necessary for proper growth. Metalhalide and sodium-vapor bulbs also provide sufficient light without needing to be so close to the plants. One of the best types of artificial light you can provide for your orchids is by using L.E.D Grow Lights. If the leaves are turning much darker, check whether your plant is getting enough Sunlight.
Oncidiums can be found in many habitats, from semiarid subtropical lowlands to cool and misty cloud forests. Generally, the most popular oncidiums, which feature small yellow flowers, large pseudobulbs, and strappy leaves, are intermediate to warm orchids.
Thus ideal requirement are, Day temperature at 26-30° C and Night temperature at 13-16° C. Temperatures up to 35-38° C are tolerated if humidity and air movement are increased as the temperatures rise, a good general rule in any case. Do not expose them to cold drafts or temperatures below about 10° C as that may cause the plant to slow its growth if exposed long.
It’s important to know how to water your Oncidium orchid. Overwatering as well as underwatering are common mistakes. Oncidiums generally have different water requirements during different stages of their growth, but a rule of thumb is that they should never be overwatered. Oncidiums store water in their pseudobulbs, making them more tolerant of dry media than wet. Generally speaking, Oncidium orchids require the most water when they are starting to grow and beginning to blossom. This is the only stage in which they require relatively lots of water that should be provided. After this stage, it’s best to provide less water.
Oncidiums actually love water, but the trick is to provide adequate drainage. If not, the roots will drown, lose oxygen and rot. This will make the orchid die. For this reason, overwatering is not a good idea for these orchids. On the other hand, if you notice that the top compost is completely dry, it’s usually a sign you should water your orchid again. The frequency of watering varies with respect to the media used , surrounding temperature and the ventilation provided. A way to check the mix for moisture is by sticking a wooden pencil into the mix about 3-4 inch. When you pull the pencil out, check the wooden end. If it has turned dark in color, the mix is still wet and you should wait a day or two. Oncidiums prefer clean water without a lot of mineral content.
In the winter, reduce watering to bimonthly or less. They can withstand considerable drought because of their large pseudobulbs. Wrinkled pseudobulbs generally indicate a lack of water.
Oncidiums need specific humidity levels, at least between 40% and 50%. However, these plants love humidity, so the ideal is actually between 55% and 75%. If you can’t provide that, make sure that humidity levels never drop below 40%. The higher temperature rises, the higher must be the humidity of the air, and the higher the humidity of the air, the more often and longer it is necessary to ventilate the room where the orchids are kept, otherwise there is a high probability of decay and appearance on the leaves of various fungal diseases.
Using a Humidity Tray is one of the best ways to achieve any humidity level. These trays are nothing more than a water-holding tray filled with gravel. The gravel-filled trays are filled with water to a level just below the surface. To prevent plants sitting on constantly wet gravel the plants are placed on small saucers or pieces of plastic or metal grid placed on top of the trays. A plump lead pseudobulb indicates a well-hydrated plant.
Oncidiums are magnificent in bloom. A large, well-grown plant might yield six or seven-branched sprays of yellow flowers. The effect is very much like a cloud of buttery butterflies. The most popular species include O. Leucochilum, O. Longipes, O. Sarcodes, O. Pulchellum, as well as many hybrids. Although oncidiums are known for their yellow flowers, other varieties are available. The O. Sharry Baby is sometimes called the chocolate orchid for its sprays of brownish flowers with a rich cocoa scent.
Depending on the variety the flowering season can be at any time of year, but is generally heaviest in the fall and spring. Many hybrids can bloom 2-3 times per year. In order to initiate the flower spikes, it is important to grow the plant in an area where the night temperatures fall below 18° C. Usually plants growing by a window are a couple of degrees cooler than the rest of the house. The flower spikes on Oncidiums generally grow to a medium or tall length and branch out in several directions.
"Keep a close eye on the spike when it begins to produce flower buds for aphids"
These types of orchids need enough food to thrive. It’s therefore important to fertilize them regularly or they will be unhealthy. However, over fertilization is bad for your plant. If skies are cloudy, applications once a month are sufficient. Make sure to clean any salt deposits on monthly basis in order to avoid burning the Oncidium orchid’s roots. On its growing phase, avoid excess usage of high phosphorous based Fertilizers.
Balanced Fertilizer for Growth: 20-20-20 (NPK) – 2 grams per litre of water – Spray once in every alternative weeks (14 Days) - On Blooming Periods (Once in a Month)
High-Phosphorus Fertilizer for Blooming: 0-52-34 (MPK) – 1 gram per litre of water – Spray on every alternative weeks (14 Days) - Except on Blooming Period.
Potting , Media and Propagation
Oncidiums like to be slightly underpotted in a very free-draining bark-based potting media. 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. In general, only repot when necessary. Aggressive repotting can kill an orchid. Oncidium orchids have thin roots so repotting is a very delicate job. They should be repotted about once in every two years. Like many orchids, once an oncidium has adjusted to its conditions, it should not be difficult to grow.
A wrong potting medium can be very dangerous for your Oncidium orchid. These types of orchids generally require lots of food, be it in the wild or when grown in cultivation. For these reasons, the type of potting medium is very important. They can usually survive in leafmold compost but using this medium is not advisable. It’s important to use the best medium for epiphytes, such as charcoal and cocopeat or pine bark. The fibers in cocopeat will provide adequate drainage for your orchid, which is important for its growth.
Choosing a correct pot is also important. Never pick a too large pot for your oncidium. These orchids are best kept in small, confined pots. The smaller pot, the better. Large pots will often make the compost moist and very damp, which can harm the roots and make them rot.
Plants potted in a bark mixture should be carefully pulled out of the pot. Clean off the roots of the old mix, being careful not to break the good roots. However, breaking roots when repotting is inevitable. Roots that are bad and should be cut off are those that are brown and mushy or papery. Those roots that are white or tan and are firm to the touch should be left alone. Simply place the plant into a new pot, placing the oldest growth towards the back of the pot so there is room for the newer growths to develop for about 1-2 years. Oncidiums can be divided when there are 6 or more pseudobulbs. Divide, leaving 3 growths per each division.
“ After repotting, Keep humidity high and the potting medium dry until new roots form.”
Pests and Other Oncidium Related Problems
Fungal and Bacterial Diseases of Oncidiums are common because of the levels of humidity and substrate they need to survive. Fungal agents cause problems like root rot, leaf spots, leaf blights and spots on flowers.