As a tropical plant, mandevilla cannot survive in temperatures under 55 F. To winterize an outdoor mandevilla, dig it up, plant it in a pot, trim the vine, and bring it inside. Store it in a cool, dark place.
If the plant is in the ground, dig it up before the temperature drops below 60 F, taking care not to harm the roots. Pot the plant in a container to bring indoors.
Trim the vine to within 8 to 10 inches of the soil. Check the remaining vine thoroughly. Inspect for pests, and remove them if necessary. Water well to rid the soil of any bugs.
Store the plant in a cool, dark location where the temperature ranges 55 to 60 F. Attics, crawl spaces or basements are ideal locations. Watering should be minimal; keep the soil fairly dry. Do not fertilize the mandevilla during the winter.
Move the plant to a sunny, indoor location in the early spring. Pinch shoots as they grow to help the plant fill out. Before moving the mandevilla outside in May or early June, repot the plant and fertilize it. Do not place the mandevilla outdoors until the chance of frost is over.