I was going to start putting my phal outside to encourage a flower spike, but it was about 45 degrees last night, and I was worried that might be too cold. How cold can a phal get before it's unhappy? (Well, technically, it's a doritanopsis).
I would guess you were safe, but I wouldn't go below 45 for very long. Believe the temps last night were brief, so the 45 might not have been a problem. Generally the warm orchids like Phals and Paphs don't want temps that cold. I'd say 55-60F is pretty safe for them.
I've taking a few phals down 58 to 60 a few nights with dry media. I wouldn't go any further then that.
It was only 4 nights but the leaves look bent for about a week afterwards. Anything below 60 is too cold (imho)
The phal in question is still growing some new roots after being trimmed back quite a bit and repotted due to root rot. Should I even be trying to encourage it to grow a spike, or should I be keeping it in the conditions required to continue growing new roots?
We don't have very many colder nights here but when I do have to warm up the orchid room, the heater is set at 48...which is 2 degrees lower than what it should be for the vandas but they seem to be okay.
I would think 45 for a short period of time (a few hours) wouldn't hurt but I wouldn't want any chid out in that temp for very long
The phal in question is still growing some new roots after being trimmed back quite a bit and repotted due to root rot. Should I even be trying to encourage it to grow a spike, or should I be keeping it in the conditions required to continue growing new roots?
I would wait for new roots and leaves....flowering can take a lot out of a weak plant.
I live right next to you and I have never needed to put my phals outside to get them to rebloom. I leave a small window open (with fan on ledge) to bring my spare bedroom down to 50-55 during the fall nights and that seems to do the trick! I wouldn't worry about the condition of the plants - those that are healthy and vigorous seem to spike and those that are recovering typically will just skip a bloom cycle on their own.
I wouldn't force a week plant to bloom. If you give it the TLC it needs, you'll have a healthy plant that will give you more blossoms anyways. Double & triple spikes are always nice
I have never chilled any of my phals in order to make them bloom. They bloom twice a year without any coolish period.
I just grow them under T-8 lights.
It's good that your thinking about your 'chid long term, keep them healthy and they will reward you