When to repot seedlings

[sewagner86]

Hello!!! I had purchased some oncidums seedlings back in January. I currently have seedlings of

Sunny Daze Hilo Bay
Okika
Breathless Florence
Pacific Pagan Kilauea
Yellow Star Golden Gambol

All but the Hilo Bay are in 2 inch pots and the Hilo Bay is in a 3 inch (the plant and root system are considerably larger than the others). I have seen a huge growth in roots since I placed some sustee water meters in the pots (I was probably leaving them too long between watering.....this helped me realize I needed to water about 2 times a week).

When I was checking them out this morning, a thought came to mind. Are these going to need repotting when they meet the same requirements as, let's say, phalaenopsis orchids? (They are the easiest for me to compare as I have repotted and kept phalaenopsis orchids for a few years now). I know they have a considerable amount of growing to do, but what do you look for when you are looking to repot? I know new growth is good, but what else? Just trying to learn before it gets to the point I need to do it.

And while I have your ear, anything I can do differently? My seedling oncidiums live on a heat mat (it's cooler in my apartment and the heat mat usually helps to warm them up to about 75 in the medium during the day, it gets cooler at night). I use my little water meters to help gage when I need to water (once they say it's dry, I usually wait a day before I do it). I have a grow light over top of them that automatically times for it to come on for 13 hours out of the day. I also got a little diffuser I run round the clock to help bring up humidity in that area. I think the plants look happy and healthy, but honestly, I only have experience with them since the end of January.

Thanks for your input!!

[My Green Pets]

I think they look good, and I would leave them to complete one more full growth. On the next growth, I'd think about repotting. I think that keeping them slightly underpotted is a good thing. Nice growing!

[estación seca]

They are ready to repot when new root nubs are just showing. Most of the ones you're posted are too far along. That said, they won't truly need repotting until they outgrow those containers, or the bark becomes old. They will outgrow the containers first.

I would keep them moister than you are. They will grow very much faster. Seedling sized plants of these do better with me if they never even get close to dry. My growing conditions are probably warmer and with lower humidity than yours, but I would need to water Oncidium seedllngs of that size and in bark every day or two for best growth.