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Keep Healthy Oncidium Orchids

Keep Healthy Oncidium Orchids

Oncidium Orchids are naturally found in the warm temperate regions of the Americas from Florida to Argentina. The varieties most often sold here produce long arching sprays of numerous, exquisite yellow flowers variously speckled with brown, burgundy edged with yellow (often referred to as “wildcats”), creamy-white and light burgundy, and purple and white. Blooms are much smaller and more delicate looking than on a Phalaenopsis but similarly they appear to be hovering.

Oncidium’s nickname is “dancing lady” or “dancing doll”. All orchids can be divided into 2 major groups depending on how they naturally grow, known as “epiphytic” and “terrestrial”. Oncidium Orchids are epiphytes, and will naturally cling with fleshy roots to a tree or rock. These exposed roots are frequently misted with dew or rain but they dry out quickly because they’re exposed to the air. Terrestrial Orchids grow directly in soil on the forest floor and prefer evenly moist, but not soggy, conditions.


• Depending on the particular variety, Oncidium Orchids like bright to nearly full sun. Most will flourish with one to several hours of direct sun a day.

• Generally, thicker-leaved plants can stand higher light levels.

• Grow oncidiums in an east, south, or west window.

• Oncidiums can also be grown under artificial light. Place orchids 15-30 cm (6-12″) below 4 fluorescent tubes.


• Oncidiums like 13-15°C (55-60°F) at night and 21-29°C (70-85°F) during the day.

• They will handle higher temperatures if humidity and air circulation are increased accordingly.


• Oncidiums have pseudobulbs that actually store water so they require less watering than thin leaved or thin-rooted orchids.

• Water Oncidiums thoroughly when the top half of the potting medium has dried out. This may be every 2-10 days depending on weather, pot size and type of potting medium.

Want to grow Phalaenopsis Orchids too? Click here.

• Water less when the orchid appears to be resting.

• If the pseudobulbs begin to shrivel, water more often.

• Be sure your Oncidium has excellent drainage as its roots don’t like to stay wet.


• Humidity should be between 30 and 60%. Many Oncidiums require less humidity than other orchids.

• Place plants above moist pebbles in trays with as much ventilation or air movement as possible, without any cold drafts. This promotes rapid drying after watering and minimizes the chance of rot. Or you can mist the foliage and aerial roots in the morning especially during periods of hot weather.


• Fertilize regularly while plants are actively growing.

• Apply a 30-10-10 fertilizer twice a month for Oncidiums planted in a bark-based potting medium.

Confused about fertilizer? Nurture your green thumb knowledge here.

• For plants in other media or mounted on bark slabs use All-Purpose 20-20-20 twice a month.



• Re-pot Oncidium Orchids at least every 2 years in spring when new growth is 5-7 cm (2-3″) tall or when new roots appear.

• Remove all the old mix and any dead roots.

• If dividing the orchid, keep the division in clumps of 3-5 mature pseudobulbs.

• Use a medium grade orchid bark.

• Spread the roots over a cone of potting medium and fill in around the roots.

• Maintain a high humidity level but keep the potting mix barely damp until you see new roots penetrating the bark.

• Once the new roots have penetrated the bark, resume normal watering and fertilizing.

What to Watch for

• If leaves start lightening, bleaching out, or burning, the orchid is getting too much light.

• Pests to watch for are scale, mealybug, and spider mites. Remove the first 2 with a cotton swab dipped in rubbing alcohol. Control spider mite with Safer’s Trounce.