Oncidium care

[james mickelso]

Oncidiums are easy to repot as long as you follow a few simple guidelines. Here are some basics. They don't like to be repotted very often. Do it at the wrong time and they will sit and sulk. The correct time to repot them is when their new growth has started growing roots and these are an inch long. Why? Because the new growth feeds off the older pbulbs and until their roots get long enough to absorb water they depend on the old growth. When you repot the old roots are disturbed and can't supply water as well. So it is imperative to be as careful as possible with the roots at any other time. Ok. Get the pot you are going to repot this into, one that is not much larger than the one it is in right now. Oncidiums don't like to be in too large a pot. Have the potting media ready and make sure it has soaked for a couple hours. You can use media that is dry but for oncidiums I like to have presoaked media because oncidium roots don't like to dry out. Here's another piece of information about oncidiums. They have very thin roots and lots of them. They do not like to be kept wet. They like to dry out fast. But not completely dry. Just damp. Medium sized bark with sponge rock or sphagnum moss mixed in is my favorite. Not a lot of moss but about 3 bark to 1 moss. Chop it up about 1/2 inch long. Let your plant dry for a couple of days. Dry roots are more difficult to break. Take your plant out of the pot andn get as much of the old potting media out of it as you can without doing too much damage to the roots. You don't have to get it all out. Once the roots are free of old media wash them off under the sink faucet. Now hold the plant in the pot about where you want it to be when finished. The newest growth should be about 1 inch under the finished media level. Let the roots hang down into the pot and put a handful or so of media into the pot around the roots. Now tap the sides of the pot to help settle the media around the roots. Put some more mix in and tap the sides of the pot. Keep doing this until the level of the media is about 1 inch above the base of the newest growth. Now water well and put in a bright sunny location with a little air movement. Water it when it starts to get dry. I hope this helps. Let us know if you need help.

[Dendy83]

This is very helpful, James. Thank you very much. I just did a forum search for Oncidium care and this came up.

[Edwin Reffell]

With my apologies for total lack of photographic skill here are pictures taken by webcam today of my Oncidiums. I divided and repotted the one I was given. They are of potting mix (the same for both), roots and plants. Please tell me what they require during the winter and what is optimum care to get them to bloom much and long. I have just started spraying them with water now that I read about that the other day. How often should I mist them? It is light between about 8.30 a.m. and 3 p.m. I have an extra light tube for my plants evenings and nights. Is that good for Oncidiums and Phaleonopsis? It brightens up the kitchen where I sit at my computer. Thank you for your help.

[LovePhals]

I think the light you are saying is appropriate. I agree that Onc's are one of the easiest to grow if you give them enough water. They do have thin roots and therefore need watered more or they will dry out. The only time you need to mist is roots only that are above the mix so they do not dry out if you have them in the home with heat on. The heat makes your humidity drop and the roots dry out quickly. The one's that I have had go down hill has been from under watering. If you underwater your leaves will fall off and the bulb die back to try to sustain newer bulbs. As long as you give enough light and water they should bloom well. You know you need to water when the bulbs begin to shrivel a bit. Oncidiums are one of my favorites for their ease of growing once you get the watering down. The oncidiums I have flower as the new growth is maturing.
Luckily mine haven't been sensitive to type of water. I just water with tap water (maybe it's good I have no idea) and add a bit of fertilizer to it every couple weeks.

[Edwin Reffell]

It is 22 and a half C where my Oncidiums are. Is that the best temperature for them? I am unsure as to whether they like a cool period in the winter or not. Just now I sprayed the roots. Should I do that daily? The pseudobulbs look wrinkled to me all the time, even after I water the Oncidiums. Am I doing something wrong? They were wrinkled when I was given this orchid. I want to give my Oncidiums optimum care so they will flower.

[clusty]

Wrinkled onc. bulbs will rarely plump up again.
overwatering has a lot of times the same symptoms as under-watering. Best way is to either observe the roots with transparent pots, or insert skewers.

[My Green Pets]

Hello mr Reffell,

I am also a new oncidium owner. The folks here on the orchidboard have been very helpful in assisting me with my plant since I bought it in July.

Your plant looks like it was underwatered before you got it. Those shrivelled bulbs, as I understand it, will never regain their former size. The new growths, however, should develop nice, plump bulbs if the roots are kept moist (not wet).

I fertilize mine once every three weeks or so now that it's cooler and the days are short. According to advice given to me here, these plants don't really rest in winter, they just slow down because of the natural decrease in daylight and temperature, so that will mean less water and less fertilizer. Mine is continuing to grow with two new pseudobulbs coming up, but I've been told that I've got 6-8 months of waiting till they mature!

[Edwin Reffell]

I have cut away all the brown and black roots on the larger plant. There are only a few roots left but they are healthy. The orchid pot it was in is too large and misted rather than transparent. I have no smaller transparent orchid pots so I adapted a coffee beaker and cramped it into it and I can see the few long white roots. Perhaps it will be more humid there too. I consider it a great improvement. The Oncidium looks happier now. I made lots of drainage holes round and in the bottom and for humidity and to prevent it from reaching any water in the outside pot that is covered with terracotta balls (called leca balls in Swedish).What do you think? Now I shall check the smaller plant.

[flexdc]

Hello Edwin,
I pot mine in a fine grade bark but usually in smaller pots, just enough to fit the plant.
I live in Southern California and we grow all oncidiums in partial shade and outdoors all year long. Our sun is very strong year round. But considering your location, even full sun in winter indoors will not harm them, but make sure to adjust it gradually to higher light levels.
As far as temp, I find that they are very tolerant - from a high of 30c plus to as low as 8c will not harm them. I don't separate warm or cool growers, they all live in the same location with the temperature range I mentioned above. The exception is Tolumnia with is not true oncidiums. They were called equitant oncidiums before.
In some of your photos I see that they are planted in large chunks of bark. I would switch to a finer grade, and at max once a week watering with the finer grade potting medium.
I hope this helps.
Andrew

[Edwin Reffell]

Here is the smaller plant, cramped in a similarly adapted fully transparent beaker. I have cut away all the bad roots and left only the healthy ones, a few of which are a nice green colour. The smaller plant has more roots than the larger. It looks happy now and I am satisfied. I hope both Oncidiums will grow lots of good healthy roots, develop smooth pseudobulbs and flower. I do not have a wooden skewer so I hope a chopstick will do to see when the Oncidiums need watering again. Previously I watered when I thought they looked dry, so I have probably underwatered them. I hope I succeed with the chopstick method which I have never tested before. How far down into the bark mixture should I stick the chopstick to see if they need water? The growing medium I have used is called orchid mixture. It is expensive and I do not know of any other mixtures for various orchid species.