Thanks so much for all the answers and advice!
To WhiteRabbit -
I said regular potting mix because it had the little balls of Styrofoam that I associate with MiarcleGro-esque potting mix. I didn't peel any little bits of it off the overall ball of roots / dirt to see if I could tell what else was in there, but I didn't see any obvious chunks of anything bigger than the the little white balls.
Right now I water once a week, occasionally once every other week (if I forget the week before, not because I'm closely monitoring!).
To SJF -
Whatever it is currently potted in is quite fine, whether something that started bigger and got broken down or something that started small and is still small. It's not mud, but definitely not what I would associate with any of the descriptors of good potting medium for an epiphyte!
To james mickelso -
I don't think it necessarily needs to be repotted right away. It is putting out new growth which to me says that it's fairly happy at the moment. It's just that when it started to show new growth I realized that I wasn't just slowly killing it (my past experience, although one did tank dang quickly
) I figured I should look into how to care for it beyond remembering to water it. That's when I looked more closely at the pot and planting medium.
I pulled it out of its pot (it was dry and I kinda rolled the pot around to loosen it from the pot, so I was able to pull the whole contents out in one lump) and that's when I really noticed how fine the potting medium is. I also noticed a lot of roots were wrapped all the way around the pot about halfway down the pot, where the little slits for ventilation in the plastic pot are. Normally wrapped roots means rootbound, but I wasn't sure what that means in an oncidium. I know some plants (like my amaryllis collection) like to be jammed in small pots, so I wasn't sure what that meant. I figured I should go by the general rule of "don't repot anything in a growth / blooming phase" but again, my two past dead oncidiums led me to think that I should maybe be more careful!
I'm at work now, so I can't post a picture but I will try to get one tonight.
Again, thanks so much for all of the advice and comments! I will check out the links you all mentioned, too.
Happy Monday!
- Carrie