What is too cold for a G. Rosea?

[cold blood]

Rose hairs are fine with anything over 60, you currently have zero concerns with your temps. Night temps can even fall into the 50's without issue.....I wouldn't worry about it at all if I were you.

 

[BobBarley]

For a year or two I've been keeping my (admittedly) small t collection at about the lower 60's at night in the winter. Not ideal, but no deaths thus far, just perpetual premolt with almost all molts happening in the summer-spring time. This year however I'm probably going to invest in some form of heater as my collection is probably going to grow quite a bit.