My 10 years old tangerine (unk variety, Stark Bros) is grown in a 14" pot. It has little fruit on it, which we will eat just as a novelty. Normally through winter, I have it in my 58F basement where it gets a bit of sun through a high window. This year the autumn temps have been mild so I've been bringing it into the house on chilly nights, and putting it back outside for the warmer days.

I'm wondering what temperature the tree needs to actually make use of that sun and to not get root damage, also to be able to take up water. The pot is white, so it does not warm the soil well in chilly weather.

If 45F is not warm enough for photosynthesis, I guess I should just get the tree down to the basement till spring.