Winterize the tropical mandevilla vine by planting it in a container and bringing it indoors during the winter when the temperature drops below 60 degrees Fahrenheit. After bringing it inside, prune it down to between 10 and 12 inches, and place it in a dim area where the temperature hovers between 55 and 60 F. Reduce watering, and stop fertilizing the plant until the spring. Only water the plant enough to keep the soil from completely drying out.
To overwinter the tropical mandevilla vine as a houseplant instead of a dormant plant, trim it, and place it in a sunny spot such as a south-facing window at room temperature. Water the plant every week. In the spring, transplant the mandevilla into a larger pot if necessary, and return it outside only once the temperatures are consistently above 60 F. During late winter, feed the plant a diluted phosphorus-rich 10-20-10 fertilizer. The plant should start putting out new growth before the time comes to return it outdoors in the spring.
Winterize a mandevilla in the ground by digging up the rootball and placing it in a pot. Water the roots well to get rid of any pests before moving the plant to a dark, dry area.