Supreme Commander Harry Tolen (Chula Orchids) put down a little
ditty about orchids that did well in his neck of the woods (Chula Vista,
CA):

http://members.cox.net/lmlauman/osp/...h_orchids.html

There's also the old r.g.o. article on arid-growing orchids that I
archived he

ftp://ftp.nmt.edu/pub/orchids/arid_orchid

Sheri Musil noted that Onc. cebolleta is epiphytic on cacti in
Mexico; however, this is under unusual conditions of humidity and
condensation. I've wanted to try some out here, but not had the chance. I
have them in flask, but I think they'd expire horribly unless they were
gradually acclimated, and I just didn't have the time this spring.

In general, as thick-leaved orchids are CAM plants, most will do
just fine with low daytime humidity. Thin-leaved orchids are another story
entirely.

Cheers,

-AJHicks
Chandler, AZ