Gardeners love to save plants from year to year. The frost sensitive mandevilla is at the top of many gardeners list of plants to save.
You can bring the whole plant indoors and grow it like a houseplant. Just isolate for a few days and check for insects before adding it to your indoor garden. Grow your mandevilla in front of your sunniest window and water thoroughly as the top few inches of soil begins to dry. Don’t be alarmed if your plant starts dropping leaves as it adjusts to its new location. New leaves will soon appear. Don’t fertilize until late winter unless the plant starts producing new growth or shows signs it needs fertilizing.
Or store your plant in a cool, frost free location for winter. Water your dormant plant occasionally to prevent the roots from totally drying out. In spring, move the plant to a warm sunny window, start watering regularly and fertilize with a flowering plant fertilizer.
A bit more information: Don’t give up if you fail at your first attempt, I did. But once I found the right location, I was able to keep a plant growing for quite a few years. And each year I added a new variety or two to my collection.