A few leaves on the oldes pbs could yellow normally. But the yellowing shouldn't continue and continue.

My guess would be dying roots. This could have begun before you even bought the plants, and is really quite a common thing in new plants that were heaven knows where before you got them, so don't get on a guilt trip. Focus on restoring the plant's vitality, which you can fairly easily do if they aren't too far gone.

When roots are compromised, plants start to discard leaves. My advice would be to stop trying to get more blooms. You won't get them on an ailing plant. Also, many oncids bloom twice a year, but others only bloom once, so you can't expect new blooms til at least next summer, maybe next fall.

Concentrate on restoring the plants to health, and they'll bloom for you, probably next fall.

I would take them out of the pot and examine the roots. If the roots are good, make sure the pot isn't too big for the rootball, and that the drainage is good. Also make sure you do not plant it too deep-- *all* of the pbs should ride just on top of the medium, not *in* it.

If the roots are bad, oncids re-root quite well in a clay pot with a little lava rock on the bottom, and then a thin layer of sphag over the lava rock. Water when the sphag is crispy. This creates a nice humid atmosphere around the the plant, and fosters new roots.

New roots form only on the newest pbs, so I would also put rooting hormone on the newest pbs, at the bottom of the curve on the pb, where roots will appear.

Give them the best light you have. With rooting hormone, it can take as little as a month for new roots to appear. Expect some action from them as the days get longer and the sun gets stronger.

Don't fertilize until the plants have roots again.

Good luck.

I find they do not require direct sun at all, mine get bright indirect light only. I have mine in sphag and water when it gets almost dried out. I feed during the growing season with half strength miracle grow. By the way, Miracle grow has a new formula I understand so read the label!

Can you post a picture of your plant? That might give us a sense as to whether you have too much light, whether the leaves are actually dying, burned, or what. I find that it depends on the oncidium how much light it likes. My sharry babies take full sun until mid summer, then they burn, otherwise they can't get enough light. Other oncs, however, seem more sensitive (mind at least are). So, it could be too much light IF the leaves aren't actually dying, but are simply turning yellow. Or the leaves may be dying because the roots are dying, or a mineral problem or lots of things. Definitely post a picture or a few if you can.

I don't know what LoE glass is, but maybe it blocks the light?? It could be you are fertilizing too much. If they are not making growths, why would you fertilize at this time of the year? Oncids are tricky with fertilizer and water quality. If you water is too hard it could affect some plants.

If the leaves are yellowing and falling off, that is not a light issue. Sounds like roots. Cut back on fertilizer and water when the media is almost dry.

Post a few pics.

Jane

In my oppinion it sounds like (mostly) a light problem...too little. between living in z-5 and having low-e glass the weak winter sunlight isn't enough for your oncs. I would increase the time the cfls are running to about 9 hours at a minimun and make sure they are no more than 12 inches from the leaves. Make the light increase slowly so you don't burn the leaves as they adjust it should take you a couple weeks to bring them up t the right light level. With the low light levels you've been giving them the roots haven't been able to propely utilize the water so by now you may have some root rot to contend with as well. Go ahead and check the roots, trim off the rotting ones and repot in good mix and in a pot that fits the root mass. The leaves that have already started to yellow will probably be lost but you should be able to save the others, and when the new growths start they'll be strong and healthy.

Sorry it took so long to get photos up. I've never done it before so hope this works. I've included many photos from different angles at the highest resolution.

Everything is in bark. I haven't repotted anything yet but they were purchased from a high end greenhouse, not a lowes or home depot.

The CFL's are putting out 2800 Lumens each. I've moved them back in case they were too much for the orchids. I've also decreased their time on, before it was about 10 hours, now probably 6 hours.

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A few observations. Your plants appear healthy. But they appear dry. I would add some sphag to the surface to maintain some moisture around the roots. The yellowing looks like sunburn or scorch, either from sun or the lights. The yellowing of the old leaves is normal. The newer leaves look scorched. What exposure is that window?

You have some wrinkled leaves which is probably due to dryness - sphag coat will help. The dry air indoors, will cause the bark to dry out quickly.

Jane

The window is northwest and starts to get direct sun (when it's out) around noon. I will get some sphag to coat the top after examing the roots. The one with wrinkled leaves was purchased that way from the greenhouse, it was the only one left. I will move the table away from the window and the back up the CFL's and hope that will provide a good balance. Thank you.

I find that my oncidium is thirsty. I water every four days in the winter, more often when they're outside in the summer. Mine are in bark mixed with some sphag and in a west window where they get late afternoon sun.