Dying P bulbs and yellowing leaves

[Imokira]

My oncidium has had yellowing leaves. 2 of the older looking P bulbs have also yellowed and died and seem squishy. Some of the leaves that are dying are the brand new ones that haven't even fully grown yet. What's wrong? I'm going to report it for the first time on Sunday. I have included some photos.

[estación seca]

What are your temperatures? How have you been watering it, and how often? How much light is it getting?

This can happen with not enough water or dead roots from old rotting potting mix. Often these are sold in flower, with the plant ready for repotting. Have you repotted it since you got it?

[Imokira]

The house is currently kept at 78°. It's kept in an easy facing window. I've recently started trying to water it twice a week because I read on oncidiums are more thirsty.. I was watering it from the tao, but last week learned my tap is hard water, so just started watering it with some rain water in a watering can from the top. I got it in flower at least 4 months ago and like I said above I plan on repotting it on Sunday. It's really concerned because a new chunk of leaves yellowed and just came right out.

[rbarata]

Your medium seems old and, by the look of it, it's suffocating the roots.

[estación seca]

I think the medium is probably old and breaking down, obliterating the air spaces and suffocating roots. Oncidiums should stay moist and not dry out. Always-moist medium breaks down faster. Most Oncidiums sold in flower were repotted about two years before, and are ready for repotting. I repot them as soon as the flowers fall and they are making new growth.

[Imokira]

Originally Posted by rbarata

Your medium seems old and, by the look of it, it's suffocating the roots.

Mmk. And that can cause the yellowing leaves and dying p bulbs? Does it look like it might be too far gone to repot?

[estación seca]

Yes, with poor roots not enough water can be taken up. Or with no air at the roots rot may enter the plant from the base. You won't know whether it's salvageable until you repot.

[Roberta]

Where there's green there's hope... the old pseudobulbs look to me like they still have enough substance to keep the plant going until it can make a new growth and new roots after a repot. THey'll end up very shriveled, but by that time, with luck, you'll have a new growth throwing new roots and it will be off and running again.

[estación seca]

Oncidiums can be heartbreaking because rot usually enters the plants through suffocated roots. The rhizome and the bases of all the pseudobulbs - with the remaining growth points - can all be dead before you notice a problem. This is one reason I usually grow them in semihydroponics: There is always lots of air at the roots.

That said, if the pseudobulbs are firm all the way down to the rhizome, there is a good chance it will survive, as Roberta said.

I have three back bulbs of a Rossioglossum cross that were completely firm, with good rhizome, when I put them into a pot about 18 months ago. I used a typical Oncidium mix rather than S/H because they were rootless, and the bases of their pseudobulbs would not remain moist in S/H in my conditions. They have done nothing. It is possible all the growth points are gone. They may sit there, photosynthesizing to keep themselves alive, for years. But I hope there is a meristem left, and something grows.

Keep in mind a happy Oncidium will grow very rapidly. You will have flowers from a miserable almost dead Oncidium back bulb long before you will have flowers from a similar Cattleya back bulb.

[Imokira]

Thank you everyone. Where is the rhizome of an oncidium orchid? I suppose I'll see how the roots are tomorrow. I'm a bit Intimidated because of how tiny the roots are and the fact that it's probably root bound. I'm afraid I'm going to do more damage just trying to untangle the roots =/.