I'm looking after my neighbors tropical hibiscus which she transplanted into a bigger pot last November. This plant is in a glass roofed sunroom and I been noticing in the last month the leaves have turned brittle and have nearly all fallen off. I realise the extreme cold winter weather is not a favorite of this tropical plant. I tested a small branch and it is not dead, even though it looks like it is. My question is what can I do too help this plant recover, or will it die because of the freezing temperatures?
I believe the following article addresses your question: https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/hibiscus-leaf-drop.htm