Oncidium Care Guide
Affectionately known as the Dancing Ladies, Oncidiums are loved for their lively, graceful blooms. In many species the lip dominates the flower, flaring out like a full, swirling skirt, with the smaller surrounding segments forming the dancer’s arms. In a light breeze, a spray of flowers sways and flutters like a room full of dancers. This diverse group originates in South America, and while some species are tropical, most prefer sub-tropical or temperate climates, making many of them well suited to Sydney growers. Whether you’re growing your first orchid or adding to an established collection, Oncidiums bring movement and charm to any display.
Light
Light needs vary widely between Oncidiums, so the first step is working out which type you have. The leaves are the easiest clue.
Thin-leaved Oncidiums are the more common type of Oncidium you will find, which have soft, flexible leaves, usually growing from noticeable pseudobulbs. These types prefer medium to heavy shade, around 50-60% shade cloth. Too much light can cause leaf spotting and burning.
Thick-leaved Oncidiums include the mule-ear and equitant types, such as Trichocentrum & Tolumnia. Mule-ears have one or two stiff, leathery, upright leaves shaped like a mule’s ear, with small or no pseudobulbs. Equitants are small plants with flat, fleshy leaves overlapping in a fan. These types handle bright light and nearly direct sun. Aim for around 20-40% shade cloth, letting through about 60-80% of the sun.
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Most Oncidiums will thrive with 1-5 hours of good light a day, and more light typically means more blooms. Foliage is your go to indicator to determine if your orchid is receiving enough light!
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Leaves should be a medium to light olive green colour.
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A shorter, stocky plant, with light green to yellow leaves suggests too much light and risks burning the plant.
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A tall, spindly plant with dark green leaves indicates too low light.
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When growing indoors, an East, North, or West window that provides 1-5 hours of bright, filtered light is ideal. Avoid direct sun on the plant, particularly during the middle of the day. Many Oncidiums also grow well under artificial light. Place LEDs or bulbs 30-60cm above the plant, providing around 10,000 lux (about 900 foot-candles). Growth is possible at around 1,000 lux, though flowering may be poor.​
Temperature
Oncidiums will grow well in the intermediate conditions of the Sydney region. They'll grow well if given some extra warmth, preferring ideal day temperatures of 27-29°C and night temperatures of 13-16°C. They don’t need a seasonal temperature change to trigger flowering, and they are happy indoors at room temperature.
Most species grow well down to 10°C and will require particular attention and reduced watering during cooler temperatures. Oncidium also require protection from frost.
Oncidium can tolerate heat up to 40°C, as long as humidity and air movement increase as the temperature rises. In hot weather, increase watering and make sure plants cool down to 21-27°C overnight.
Watering & Humidity
​​Watering
Thin-leaved Oncidiums have thin, small roots that appreciate more frequent watering than their
thick-leaved Oncidium cousins, which have thick, fleshy roots and need less frequent watering. When watering, water thoroughly, then let the medium approach dryness before watering again. Depending on weather, pot size and potting material, this may be every 2 to 10 days.
Some Oncidiums have a substantial rest period, some a short one, and some none at all. Water regularly while growth is active, then sparingly once growth has matured and during any rest period.
Too little water, too long between waterings, or overall irregular watering may cause pleated “accordion” leaves and growths. This can be fixed by adhering to a regular, appropriate watering schedule.
Avoid wetting the foliage, as Oncidiums are susceptible to various fungal infections and leaf spotting.
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Humidity
Many Oncidiums need less humidity than other orchids, with 30-60% ideal. Indoors, standing the pot above moist pebbles in a tray helps. Provide good air movement if conditions are damp or
humidity rises above 75%.
Air Movement
Just as we appreciate opening a window for fresh air, orchids enjoy gentle air movement at all times. If you feel comfortable, so too do the orchids!
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Good air circulation is essential for Oncidiums. The air should be moist and gentle, as no orchid likes a draught. Air movement helps prevent rot and fungal growth, and helps strengthen plants as they grow. An open window during the day or a circulating fan will bring out the best in your Oncidium. In hot weather, increase air movement along with humidity to help keep plants cool.
Fertilising
​Oncidium are moderate feeders that enjoy a constant, mild fertiliser with every watering. A regular feeding program of a balanced fertiliser (12-12-12) will help promote growth, flowering and strong plants.
Fertilising regularly during active growth will help produce strong pseudobulbs. Once growth slows, reduce or briefly stop fertiliser so to not push new growth during the cold months of the year.
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Remember: weakly weekly!
(It's better to fertilise lightly every week than to feed heavily once a month)
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There are many commercially available fertilisers that all work in differing ways:
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Slow release granular fertiliser releases a small amount of nutrients over a long time (3-6 months) to ensure your orchid is always fed.
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Liquid and dissolvable fertilisers provide water-soluble nutrients directly accessible to your orchid, giving them an immediate boost. Many are fortified with seaweed solution as a plant health tonic.
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Organic fertilisers, such as blood and bone, are not recommended for orchids as they require soil microbes to break down their chemical structure before a plant can use the nutrients.
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Always start at 1/4 to 1/2 strength of the commercially recommended dose to avoid fertiliser burn.​​​
Repotting
How often you repot depends on your growing medium. A mix with sphagnum moss retains more moisture and breaks down faster than a mix of orchid bark, charcoal, and perlite.
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As a general rule, repot Oncidium every 2-3 years, both to refresh the medium before it breaks down and rots, and to give the plant room for continued lateral growth.
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Repot when new growth begins, usually in spring, and up until the new growths are half matured. Oncidiums initiate new roots early in their active period, so plants recover quickly with minimal setback. Do not disturb a plant that is in flower, in spike, or in its rest period. Avoid repotting during the middle of Summer, or during Winter when the plants are usually resting from active growth.
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If your plant has become large, or is outgrowing it's pot consider whether it's appropriate to increase the pot size or to divide the plant. If you choose to divide your Oncidium, use a sharp, sterilised tool to divide the plant, leaving groups of at least 3–5 bulbs together per division. Aim for the higher end where possible.
Discard any old, brown or soft bulbs, and remove any dead sheaths and leaves, as these harbour pests such as scale. Remove any dead roots, particularly from old back bulbs.
Repot each division in separate pots. Expect a delay before flowering after dividing, as plants will need to regain their strength to produce their spectacular displays.
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Never reuse old potting media.
Sterilise all tools and any pre-used pots with 10% bleach concentrate before use.​
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Thin-leaved Oncidiums have fine roots that die quickly if the medium turns soggy, so fresh, free-draining medium matters. A good mix is 50% medium-sized orchid bark (8-15mm) and 50% pumice, charcoal or other inert media that opens the media so it stays breathable and drains well.
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Thick-leaved Oncidium with large roots can be grown on slabs of cork bark or tree fern. However, many growers pot their Oncidiums in pots of coarse, well-drained bark (12-18mm) to stop them drying out.
When repotting, position the newest growth away from the edge of the pot, leaving room for as many new growths as possible to form in the centre as the plant expands. Spread the roots over a cone of medium, fill in around them, and firm the medium around the roots.
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After potting or dividing, water well, then move the plant to a cool, shady position for one to two weeks to recover, watering sparingly during this recovery period.
Orchid Care Sheet
Want to keep track of your own orchid's specific needs? Download our printable Orchid Care Sheet, a handy template for recording everything from watering and temperature preferences to potting, fertilising, and flowering habits. Perfect for building your own personal care journal as your collection grows, or for jotting down notes from a Grower's Group chat at our next meeting.
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