When should I remove my purpled-leaved oxalis into green-house?
 

I heard that the purpled-leaved oxalis would die in the winter, and
will revive next spring from the tuber. However, I have an access to a
green house in my institute. So ,I hope I can move my lovely oxalis
into green house as the winter comes. But when ? or rather , under how
many degree Celsius, should I remove it?
Thanks a lot!