Answer: Keep your mandevilla in the pot. Mandevilla is a tropical plant and will not survive your winters outside -- not even with extra protection. But they can be overwintered indoors. You will need to bring it indoors, before temperatures drop below 50 degrees. Prune the top of the plant back by one-third when you bring it in and place it in a warm, sunny spot. It will continue to grow (slowly) indoors and next spring you can take it back outdoors to enjoy.
Best wishes with your mandevilla.
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