I'm repotting my Oncidium Twinkle, and I find mixed messages about what potting medium to use. Should I use a) sphag + medium-coarse bark or b) just medium-coarse bark. I know there have been problems with sphag and root rot, but it seems like a popular thing to do.
I'm still new to Oncidiums, but if I'm not mistaken they're supposed to be potted in fine grade medium. Maybe one of the more experience Oncidium owners can give you more concrete information
Jadeco it's a matter of personal choice I think. I have 2. One is growing in a fine mixture of bark and perlite, with some charcoal in a pot with side slits. Seems to love it. On the other hand, I have another that i just transferred to semi hydroponics and it's fine.