The Mandevilla plant has tubers, in which it stores food and energy. The tubers are not part of the reproductive process. To store for winter, trim, bring it inside to a sunny location, and water weekly, and the plant will grow again in spring. Alternatively, bring the plant inside to a cool, dark place and water once a month.
Key Takeaways:
- If you try and grow mandevillas from tubers you will most likely fail.
- Mandevilla tubers store nutrients for the plant that help sustain it for winter.
- Storing mandevilla tubers for winter isn’t necessary, and in fact should not be excised from the plant during winter.
“There are several easy ways to start a new mandevilla plant, including seeds and softwood cuttings, but propagating mandevilla from tubers probably isn’t a viable method of propagation.”
http://www.gardeningknowhow.com/ornamental/vines/mandevilla/mandevilla-plant-tubers.htm