if its warm enough for orchids, its warm enough for citrus.

unless you have immature fruits, then it needs to be around 80'F day time, and probably no lower than 70' night time.

Sorry- I did not include details of my setups because I did not want to complicate things :)

The orchids and lighting are in a HydroHut- an enclosed greenhouse thingamajig that keeps humidity in. The contraption sits in my garage and keeps the ambient temps up to a degree but it does get cool at night, especially outside the enclosure which is where my citrus are.

If the air temps are 35-40F I thought warmer roots would be better.
No?

if your citrus don't have any fruit on them, then 35-40F would be ok.

Thank you.