Thank you for all your comments!
That's what I liked about this site, that everyone's really helpful and friendly.
I couldn't write before, I've been really busy.
I grow them indoors, except for one. Actually, the first one I had got tipped over accidentally and the two spikes broke (less than a week after I bought it
) so I put it on a good spot on a tree. After some time I saw it was getting too much sun so I put a screen just above between the branches and solved that for good. That was last year. The plant seemed healthy and it was actually growing two new leaves. The roots weren't good though, I couldn't find any live one so I thought they were growing on the side I couldn't see (against the trunk). So pretty much nothing happened except for the new leaves being destroyed by bugs. Then, about two weeks ago, I got an orchid with great roots in a clear container and decided to take the first one down and substitute it. I did it with great difficulty--the tree had grown little roots into the orchids medium (which was turned almost to soil). It's a mystery to me how the old one is alive and looks fresh at that. I have to pot it now. The new one looks great! I took the precaution of putting it inside a coconut fiber pot with bark against the tree. So that's the really looong answer.
Shakkai- thanks a lot for the Tahi orchid site, I'm going to the greenhouse as soon as I get the chance since it's not a long drive from where I live, luckily.