Cattleya/Laelia pure indoor Culture, how important is Day/Night temp fluctuation?

[JScott]

My Catt/Laaelia types don't depend on temperature fluctuation to bloom. I grow some outside in the summer and some inside all year. The ones that grow inside all year seem to be influenced more by time of year than temperature. My plants, both those which grow outside and those inside all year, tend to bloom at the same time every year, regardless of the temperature.

I have some Catts that bloom on each new growth, several times a year, regardless of the season, and then I have those that bloom once a year in the same month each year. I wouldn't worry about it too much. If your plants won't bloom, there are more important factors to consider (light, watering, etc.).

[estación seca]

Welcome!

[Fairorchids]

You mention that the plants are small seedlings. From that stage, till they are blooming size, temperature differential is totally immaterial, since they need to grow, not bloom.

Very small seedlings (in 5 cm/2" pots) generally do better if grown under slightly higher temperatures, than you would provide to a mature plant. And, continuing this through the next stage (in 10 cm/4" pots) doesn't hurt.

Once the plants are large enough to bloom, then a 10-15 deg F (5-8 deg C) differential would be helpful, if you can manage it.