Flowering Oncidium Repot
 

I have an oncidium hybrid (recent acquisition) that needs repotting, but it is blooming profusely and still sending up new spikes. The plant itself and what I can see of the roots are in good condition but I suspect the medium is poor to the point where I don't want to risk waiting a month or more until blooming is finished.
Most advice concerning repotting a blooming oncidium that I could find just says "don't", but that is not very helpful for me.

My question concerns the spikes. Will it significantly help the plant to cut blooming spikes before (or straight after) repotting or will it not improve the plant's condition? Will the newly emerging spikes (no buds yet) be safe?
Can I induce a new growth phase quicker by cutting the spike then waiting a few days before repotting?

No doubt others will disagree... it would be best to wait. If you just cannot, repot very carefully and don't cut any thing unless it's totally rotten.

Repotting immediately is something of a judgement call.

I would first try to loosen up the potting medium by squeezing a plastic pot, or extracting the mass from a clay pot and poking a few holes to open it up. Then I'd "baby" it by barely moistening the potting medium.

If I saw issues starting, I'd chop the spikes and repot.

My inclination would be to gently repot, keep the spikes. You can slip the plant out of the pot, shake off or gently remove excess medium, then repot in fresh bark (so you disturb roots as little as possible) Many in the Oncidium tribe start to push new growth right as they are blooming (and new growth comes with new roots) so if you provide some fresh medium that those new roots will like, don't worry too much about the old stuff. The next time you repot, in a year or two, that old part will remove easily, but they that time you'll have new growth (and probably new spikes) so at that point the old stuff won't be missed.

Hmm, I would prefer to wait, but some of the newly opened flowers have suddenly started wilting (not in normal drying up fashion) while buds and older flowers and some other new flowers are still perfectly intact. The wilted flowers are all on the lowest side-branch of a long spike, though they started opening at the same time as the new flowers higher up and those are fine. The flowers on the other blooming spike are unaffected despite being at the same height. I'm worried that this could be a sign of the medium staying too moist around certain roots.
The medium is coco coir mixed with bark. I've poked around a little and the roots that I can see look good, but I'm worried it might have a ball of spaghnum packed in the middle which would explain why the top layer of medium dries out very quickly but the pot stays pretty heavy. If this is the case, I don't think I can pry out the moss without damaging any roots.

I really like this particular plant and don't want to damage it in the long run. Are my odds better waiting a short while for the right growth moment but risking potentially damaging medium rotting the roots, or just repotting right now? I'm not sure how much of a setback or energy drain it is for an oncidium (or any orchid) to be repotted while in bloom.

Perhaps I should also mention the new spike is coming from a new growth that has some longer roots but also some newly emerging ones of about an inch.

(As Ray suggested, I'll resort to only lightly misting it and waiting for the moment to see if the wilting gets worse. I've dug a little more and still only seen healthy roots.)

Repot gently... I really don't think that blooming will harm the plant - the blooms are not as long-lasting as Phalaenopsis flowers and so I think won't drain the plant significantly. but getting it out of bad medium is a good idea... just don't be aggressive about it, get rid of medium that comes off easily but don't worry about getting all of it, and give those new roots some good medium to grow into. Then you can have it both ways... good medium for the new roots, but enjoy the flowers.

As someone who loses more plants to root rot than any other reason, I will now always say repot if you think things are going sour in the current pot.

Oncidiums aare pretty hardy, and are probably not heat stressed in the NL, and not cold enough where metabolism has slowed to a crawl for winter either. If you have fully formed buds waiting to open, I'd just wait. But if they are new spikes with no buds, i'd go for it.

If you choose to re-pot, do it right.
Try to untangle the roots (gently) and get all the old media and dead roots out (within reason, use good judgement about what can come out without ruining the roots). This is sometimes a major downfall for me who hates disturbing a huge bushy root bound mess. the last thing you want is to disturb the plant with a repot if you don't actually improving the air flow to the roots and freshness of the media (don't create rot in the new pot!)