Oncidium is a genus with over 300 species of orchids within it. Perhaps the most popular and most common are the ones with flowers referred to as “Dancing Ladies” because of the shape of the pedals. They look like wide skirts with arms sticking out to the sides of what could be a “body” in the center. They generally grow from bulbs technically referred to as “pseudobulbs.” I don’t know why that name, because they appear to be real bulbs – nothing “pseudo” about them, unless they don’t do what bulbs normally do, but in this case they appear to. Yellow seems to be the #1 color I see, with dark red or brown-red is also common, as is a plant called “Sharry Baby which has this dark red, almost purple mixed with white.
Oncidiums are technically epiphytes which means they generally grow in nature upon other plants (such as trees). They aren’t parasites as such, since they don’t really “feed” off the host plant – only use it for support. They absorb nutrients through the air and rain and decaying matter and debris that accumulates around it. There have been major changes to this genus and a lot of re-categorization to a number of plants or species that were considered Oncidiums and now perhaps are not. I have a number of them where the tags have been lost and I simply don’t really have any way of knowing exactly which plant is which. But if they look like Oncidiums I treat them like Oncidiums and I consider them to be Oncidiums… Not that it matters much in a personal collection. Their care and wellbeing and appearance are all that matter. Sometimes there is a single leave protruding from the top of the pseudobulb and sometimes multiples.
I have the occasional plant that doesn’t seem to reproduce by throwing off additional pseudobulbs in the bark. These would be growths from the root system that will break through the surface and mature with new, fresh leaves on top of them. This one plant, however, is very “arial” in nature. It throws off new pseudobulbs from the joints with leaves, and the new bulbs, well above the surface of the bark, then throw off an entire root system of their own. You will see this behavior in other orchids from time to time, where “pups” grow in the oddest places, well up on stems and stalks. This particular plant gets overgrown when it’s a mass or arial bulbs and roots. When I repot this one I separate off viable plants that were growing in the air and pot them up separately. But it is clearly an Oncidium. The beautiful tell-tale yellow flowers at the beginning of this page were photographed on this plant.
The plants in this genus tend to grow by adding pseudobulbs to the pot and it simply gets more and more crowded until you re-pot and separate. You create separate plants by repotting clumps of the healthy pseudobulbs. the bulbs, like all parts of living plants, will eventually die. That’s to be expected. So if you see the occasional bulb that is dead and brown, cut it away when you repot. But don’t worry about it in the meantime. They do tend to rot, however, so I would definitely remove them when I repotted.
And as they age, the oldest bulbs also tend to lose the leaves that originally protruded from the top. As long as the pseudobulb says fat and healthy in appearance, I just ignore them. I figure if they are serving any purpose at all other than structural support for the leaves, it’s probably as a reservoir for moisture. If that’s the case, leaving the bare healthy ones can’t seem to hurt. The pseudobulbs in this particular specimen of Oncidium Sharry Baby are particularly fat and healthy, with a few having lost their leaves.
They tend to throw off long racemes, or flower spikes, and typically have multiples at a time. Some plants put on a real show and are practically covered with blooms on short racemes. Others send up a few beautiful long racemes lined with flowers. Either way they are beautiful. They are relatively easy keepers. One thing you will notice when you look at a plant and contemplate purchasing it. Some of the pseudobulbs (or even all) may appear shriveled. That is as a direct result of too little water during a critical development period. Those shrivels never come out. Once a bulb is shriveled, it will stay that way until it dies. However, that doesn’t mean the plant is not viable. I have had Oncidiums where no matter what I did and how much i watered, the pseudobulbs shriveled. Others had shriveled bulbs when I got them but responded well to good care and produced nice plump pseudobulbs after that. Unless the plant is sick, it’s all a matter of aesthetics. Nothing more.
The bulbs (or pseudobulbs) of Oncidiums are very similar to the bulbs of other orchids, like the Miltassia. However the flowers are very different. There are some beautiful crosses as well. For example the Odontocidium (pictured here) is a cross between the Odontoglossium and Oncidium orchids. This one is called Kennith Bivens. It has very “spidery” exotic looking flowers. They don’t last long but they are a real novelty that get a lot of attention when they bloom.
WATER: Water regularly. Oncidiums in general respond well to my twice-weekly watering regimen. Because of their reservoirs, they can stand periods of extreme dryness, but I try to avoid that at all cost because I simply don’t like the look of the pseudobulbs all shriveled up. And if they shrivel, the plant will look that way literally until new growth as replaced all the bulbs – and that can be a VERY long time indeed!
LIGHT: Onicdiums like light. The thicker the leaves, the more sun they can take. But most will do well with a couple hours of sunlight per day. I would still avoid the absolute harshest, hottest mid-day sun, but I avoid that with ALL my orchids. I keep this orchid in my “orchid” room in bright spots, frequently on my east-facing racks where they are exposed to direct morning sunlight.
MEDIA: They do very well in my usual coarse bark mix.
TEMPERATURE RANGE: Normal household temperature ranges. Lows should not be below the 50s and highs should be kept to the mid-80s if possible. That suits most households. They can handle extreme heat (95-100 degrees Fahrenheit) for short periods of time if air movement and humidity are increased as well. But they do very well in normal household conditions.
CARE: Easy to care for. They fit right in with my light, watering, and temperature conditions.
BLOOMING: Develops racemes of various lengths. Some of my Oncidiums create wonderful, very long arial racemes covered with flowers. Others bloom on shorter racemes where the entire plant may be more covered.
REPOTTING: I tend to repot annually with my usual coarse bark. I would trim the roots if they needed it and separate the pseudobulbs into several healthy groups and repot separate plants if they needed it. Once the pseudobulbs and leaves reach maturity, these plants will not continue to grow, they will just continue to get denser until you separate.