That's really awesome that you plan to attach some orchids to a tree! I really love seeing
orchids on trees. Plus, I'm pretty sure that they are happier on trees because their roots are free to ramble and roam all over the tree. More roots means a happier orchid. Plus, orchids on a tree have excellent drainage. And... you don't have to worry about repotting!
A while back I attached a bunch of orchids to my large Cedar tree and most have done really well. I'm pretty happy with them but... if I had to do it all over again then I'd probably favor orchids that are pollinated by hummingbirds. My hummingbirds have done a really good job brainwashing me! Each time they sing their squeaky songs it really sounds like they are saying... "We want more orchids that match our preferences!"
At the orchid show at the Huntington this last October I picked up a really nice blooming cross from SVO for $12...
Ctna. Why Not ‘Red Gold’ AM/AOS x Epc. Kyoguchi 'M. Sano' Mutation
Why Not = Guarianthe aurantiaca x Broughtonia sanguinea
Kyoguchi = Guarianthe aurantiaca x Encyclia incumbens
I've read that both G aurantiaca and B sanguinea are pollinated by hummingbirds and sure enough... when I inspected the cross's flowers a few days after I purchased it... most of the pollen was missing. Fortunately... the flowers didn't wilt and they've lasted up until just recently.
The flowers on this cross aren't very large but, thanks to the Encyclia incumbens, you do get quite a few of them. Plus... they have a nice reddish color that should stand out really well on a tree.
I'm guessing that Guarianthe aurantiaca should be fine growing 5 miles from the coast. Not sure about Broughtonia sanguinea though. It does seem to appreciate some decent heat. The closer to the coast that somebody lives... the more direct sun I recommend they give to the heat lovers.
A really nice hummingbird orchid that prefers cooler temps is Prosthechea vitellina. It's pretty stunning and I've really wanted one for a really long time but I was under the impression that my summer temps were too warm for it. A couple months ago I said heck with it and purchased one. I also managed to find a few crosses with it. Hopefully they'll have a nicely wide range of growing temps.
I'd love to try and grow Prosthechea vitellina crossed with everything. Especially other hummingbird orchids like Guarianthe aurantiaca, Broughtonia sanguinea, Epidendrum secundum and so on. Then my hummingbirds will have plenty of orchids to choose from.