Answer: Vigna caracalla can be dug and stored as one would handle dahlias. You may need to experiment to find a spot with the right temperature, somewhere closer to 45 degrees.
Mandevilla can be kept growing all winter in a very bright location, or it can be allowed to go semi dormant. To do this, trim it back, reduce the temperature to about 50 degrees, hold back on watering so that the soil is just barely moist, and do not fertilize. The plant will probably defoliate, but should return to active growth in spring when placed in a warmer bright location and watered and fertilized again.
Good luck with your plants!
Q&A Library Searching Tips