Hi there, I think you have the added advantage of being able to move the plant to a warmer location and I think I'd do that for now and cut off the leaves if or when they start to yellow.
I have one with 8 stems growing in open ground which I usually cut off the leaves when they start to yellow towards the end of october, this yeare they stayed greener for much longer and I only cut them off last week, still amazingly green and about 6ft long. I'm now covering the stems with horticultral fleece to protect them, I've gone through this ritual for about the last 5 years and so far so good.
Good Luck Tbird+