Oncidium Dancing Lady Die Off
 

Have an Oncidium Dancing Lady that's been blooming for me for at least two years off and on. Noticed some black root and rot while it was recently in bloom and decided it was best to risk repotting. I've generally never repotted a plant in bloom as I've heard it's not the best idea. I trimmed off all of the dead roots and any black root. Within 5 days of repotting the plant looks terrible. The bulbs have shriveled ed and the leaves look almost like they are dark at the base (almost "wet" looking) and they are all rapidly falling off. Curious if opinion is disease or just shock from repotting. Pictures of Fallen off leaves attached. Notice the marked dark area near the base.

Thx!
Ken

Sounds & looks pretty bad. The "wet" rot on the leaves means it's got a bacterial or possibly fungal infection. If you have other orchids, you should consider getting this plant into a quarantine situation or just toss it so as to minimize risk of it spreading to other plants.

If you want to rescue the plant, you should get it into a breezy spot with extra ventilation, and for now keep watering to a minimum. If you have access to bactericide or fungicide, you can give that a try (obviously spray outside, let it dry before bringing it indoors if you are growing it in your house). From there, you have to let nature take its course. If the infection continues to spread you may need to remove additional roots, leaves, and bulbs. If the plant is not too badly damaged and has some energy left, you'll eventually see some new growths and roots emerge. Once it's starting to grow again, you can increase watering and light, and as long as all signs of rot are gone, at that point, you can reintegrate with the rest of your plants.

Chances are, though, if this is bad enough, the plant may not live, so be prepared. Orchids are tough, but once they're weakened and come down with an infection, things can get pretty dicey.

Oncidiums are prone to rotting from the roots up if kept too wet. Once this starts, the plant is usually dead within days. Repotting every 2-3 years keeps the medium fresh and well-aerated. This plus allowing the medium to get nearly dry between watering helps prevent this sort of thing.

Are the pseudobulbs at their bases soft or mushy, and movable, where they attach to the rhizome? If so the plant is likely gone.

Any still firm at the base may recover. Cut off any pseudobulbs with firm bases. Let them dry for a day or so. Then set them horizontally on some barely-moist sphagnum moss inside a jar. The moss should not feel wet. Set this someplace bright and warm. On occasion a dormant meristem may produce a new plant, either at the base or apex of the pseudobulb. It will be at least several years before a plant rescued this way blooms again.

Thanks all! For some reason me and Oncidiums don't jive. Never had a problem with any other species but the Onc's always seem to get rot or black root and die. Just never had such a catastrophic change in a couple of days (usually takes months for my Oncs to deplete)..I always repot them in a course bark and only water once a week!!! I don't have any south facing windows so maybe they just don't get enough light. Although I've also noticed that most plants I buy from local nurseries have a terrible potting job and are already showing signs of rot...

An Oncidium in coarse bark watered once a week will slowly shrivel up and die. It will probably be a prolonged, agonizing death. Oncidiums are orchids that don't like to be dry for very long. Many people don't let them dry out at all. This means they need regular repotting so the medium stays fresh.

You may be right that most of the ones you buy are already rotting. Try and find one as soon as they get to the store, and look at the medium and roots before buying. When they are happy they grow fast and bloom a lot.