Tips on how to preserve Mandevilla through the winter months.
Mandevilla (Dipladena) are tropical vines, hardy (depending on cultivars) in zones 9-11. They tolerate a minimum temperature of 45-50 F at which time growth will begin to slow down. For winter storage keep the plant outside as long as possible before bringing it indoors. Check the plants for insects and use insecticidal soap if needed.
To winter over Mandevilla
Mandevilla can be treated as a houseplant. It may be trimmed back to make it manageable indoors and needs a sunny, bright window to flourish through the winter. Water once a week, keeping it on the dry side. You will get some yellowing and leaf drop due to lower light and humidity indoors. Don’t fertilize in the winter. In spring increase watering and start to fertilize.
2. Dormant stage
Another way to winterize mandevilla is in a dormant stage in a garage or cool basement with temperatures around 45-55F. Cut it back to about 12 inches above the soil line. Treat for insects if needed. Keep it dry but not completely dry. Check periodically for soil moisture. Mandevilla will eventually drop all its leaves. The important thing to keep in mind is that you want to keep it alive it through the winter.
In early spring, prune back any spindly winter growth and if pot bound repot in fresh soil. When new shoots begin to grow, start to lightly fertilize and move the plant to a sunny window. Pinch the new growth to get a bushier plant. Set outside when danger of frost has passed or night temperatures are above 55.