I recently made a purchase of some cattleya seedlings (some are species) and I have been doing research about when to repot and I found that you should only repot Cattleyas when they are in active growth when you just see roots coming out. My seedlings haven't arrived yet but my question is... Can I repot them right when they arrive to my own media as they usually come in deteriorated media or spahgnum which is not good for me? I also saw that mostly seedlings don't mind repotting and I saw some of the videos from Stephen Van Kampen-Lewis who repots his seedlings right when he bought them so it should be fine even if they don't have active growth?
I would if they are small. Seedlings don't follow the same growth patterns as adult plants, but as they grow larger, their growth habit becomes more cyclical as seen in adults. For me, repotting seedlings means new roots start forming within a month of the repot.
Yes but I wouldn't be too worried, they should still be fairly resilient.
Now I am making a big assumption that you plants are unifoliate Catts. If they are bifoliate, forget everything I said, because I have no experience with them and they are supposedly more difficult to reestablish when repotted.