an ES note copied

[early]

Oncidiums rot from the roots up. The usual causes are not enough air at the roots or being kept too warm. I doubt warmth is the issue here. Lack of air can happen with old compressed medium that stays wet too long, which closes the air spaces in the medium. The problem is lack of air, not water.

Oncidiums have very short rhizomes between the pseudobulbs. The rot spreads rapidly through the rhizome from the first affected growth. Typically by the time you first notice the rot the entire rhizome is affected and the plant is already dead.

I would take the plant out of the pot and use a strong jet of water to remove all old medium. Starting at the oldest pseudobulbs, cut off those that are soft and brown at the base, one by one. Sanitize your tool between cuts with rubbing alcohol or 10% household bleach. If you get to fresh green tissue at the base you can stop. This isn't likely. If you're lucky, let it sit for a few days in bright shade, repot, and hope for the best.

Sometimes all that remains healthy is an immature new growth. These sometimes will survive if they already have roots.

Sometimes all that remains is a pseudobulb that is mostly firm, with some soft brown areas at the rhizome. The new growth points at the base are usually dead when this happens, but there is another at the apex of the pseudobulb. If you wind up with a pseudobulb like this, set it someplace warm and dry and hope the rot stops spreading up from the base. If it does stop, after a week set the pseudobulb sideways on top of some barely moist sphagnum or vermiculite inside an enclosure - this can be a horizontal jar. The medium should not be moist enough for you to feel moistness but it should be enough to keep the humidity in the enclosure very high. Set it in bright shade. There is a chance the apical meristem will sprout a tiny new plant. This may take many months to a year or more.

---------- Post added at 11:58 AM ---------- Previous post was at 11:04 AM ----------

I copied your note ES for all the wonderful oncidium history of how Oncidiums grow and don't grow.

I am patient with all my other slow growers, but this rosdium was not secure in the pot. It had beautiful blooms when I bought it. I had it along with another one in separate pots in S/H.

I took it out and saw no roots except on new bulb had one root. I separated it into groups, leaving the new one attached to the mother,
I then put them in three small vases with Ph adjuted well water, 20 20 20 fertilizer weekly/weakly, and added some liquid kelp to the gallon of water.
I was surprised to see all but the new pseudo bulb rootless. After reading your above note, I understand why. All the leaves and bulbs were green and plump.
They still are, with dunking them every few hours alternating with letting them dry for equal amounts of time. The baby now has 4 healthy roots. So far so good.
My questions have to do with the group of two healthy looking bulbs but rootless. Could you give me some advice on the group of two and rootless? I have left them out to dry, but don't know for how long.
thanks ES. and anyone else that wants to chime in.

[estación seca]

Old Oncidium pseudobulbs won't make new roots. They may make new growths from the base, and rarely from the apex. These new growths will make new roots.

The best way to treat rootless Oncidium back bulbs is as I described above: Set them someplace in bright shade with very high humidity. You could stand them in a big jar on some barely moist medium, whether sphagnum or vermiculite or pumice or perlite. But it shouldn't feel wet. You're trying to raise the humidity in the jar, not water the rootless pseudobulbs.

[early]

Originally Posted by estación seca

Old Oncidium pseudobulbs won't make new roots. They may make new growths from the base, and rarely from the apex. These new growths will make new roots.

The best way to treat rootless Oncidium back bulbs is as I described above: Set them someplace in bright shade with very high humidity. You could stand them in a big jar on some barely moist medium, whether sphagnum or vermiculite or pumice or perlite. But it shouldn't feel wet. You're trying to raise the humidity in the jar, not water the rootless pseudobulbs.

Thanks, This gives me hope that the new bulb will produce more growth. I have some new jars I bought for sourdough starter. I have another Onc that is the same age. Last time I checked it was still firm in the
S/H. And I ordered some sphagnum. and charcoal along with some Best Gro Bark Are any or all of those appropriate for Onc?

[estación seca]

You don't want them drying out. People grow them in fine to medium bark, sphagnum moss, and bark/perlite/charcoal mixes. I must admit I see no point to using charcoal for anything if you have access to similar particle sized perlite or LECA. In your lower humidity conditions I would not use medium nor large bark for a recently rooted Oncidium. You'd have to water it every day. When I didn't have such a humid growing area sphagnum moss worked well for me.

[early]

Originally Posted by estación seca

You don't want them drying out. People grow them in fine to medium bark, sphagnum moss, and bark/perlite/charcoal mixes. I must admit I see no point to using charcoal for anything if you have access to similar particle sized perlite or LECA. In your lower humidity conditions I would not use medium nor large bark for a recently rooted Oncidium. You'd have to water it every day. When I didn't have such a humid growing area sphagnum moss worked well for me.

I was thinking the same thing. How soon should I pot the little one, now or wait until the roots are stronger.. The 4 are abt 3/4 inch.

[estación seca]

Pot now. The shorter they are the less chance of damaging them and the faster they get into the new medium.