That's a magnificent tree ! How lucky for it that you have such a wonderful space for it.
My grown from grocery store lemon tree is very small -- I've had it for a while now but don't know exactly how long, and it bloomed a single flower for the first time this winter:
So I probably can't help much -- when do you have the tree brought inside? I wait to bring the lemons in until the outside temps are in the... I think under mid-40's.
...I had to go check my own notes...
Subject: Minimum Night Time Temperatures - bringing plants inside
Yep. 45Â°F or above. My understanding has always been that the citruses prefer to stay on the cool side during the winter months. But I recently learned that some greenhouses keep them at around mid-60's which is warmer than I was trying to manage and actually more do-able for me. My trees get supplemental light in what would be way too dark locations and stay in the first floor rooms where winter thermostat keeps the temps at around mid- to upper 60's.