The Mandevilla vine, known for its striking trumpet-shaped blooms and glossy foliage, adds a tropical feel to summer gardens and patios. This plant is a perennial only in the warmest climates (USDA Zones 9 to 11) and cannot tolerate temperatures below 45° to 50°F. For gardeners in cooler regions, winter survival requires bringing the vine indoors, as a single frost can destroy the plant. The good news is that saving your Mandevilla allows you to enjoy its beauty for multiple seasons.
Dormancy Versus Active Winter Growth
When overwintering Mandevilla, gardeners choose between two distinct strategies: maintaining active growth or forcing dormancy. The decision depends on the available indoor space and light conditions you can provide. Maintaining active growth treats the Mandevilla like a houseplant, requiring a warm, bright environment to continue slow growth throughout winter. This strategy suits those with sunny, south-facing windows or supplemental grow lights. Forcing dormancy involves moving the plant to a cool, dark location, which reduces energy and care requirements. This low-maintenance method is ideal if you have limited space, such as a cool basement or a frost-free garage.
Preparing the Plant for Indoor Transition
The timing of the move indoors is a determining factor in the plant’s winter success. The Mandevilla must be inside before the first frost arrives. The ideal transition time is when nighttime temperatures consistently fall below 50°F, preventing cold stress on the tropical plant.
Pruning is necessary before the move, regardless of the overwintering strategy. Cut the long, twining vines back substantially, typically by one-third to one-half, to make the plant a manageable indoor size. This also reduces the foliage the roots must support during lower winter light conditions.
A thorough pest inspection is critical to avoid infesting other houseplants. Examine the undersides of leaves and stems for common pests like spider mites, whiteflies, and aphids. If infestation is found, treat the plant outdoors with horticultural oil or insecticidal soap before bringing it inside.
Providing Proper Indoor Winter Care
The care routine depends entirely on the overwintering strategy you selected.
Active Growth Care
If aiming for active growth, place the plant near a bright, sunny, south-facing window for maximum light exposure. Keep the temperature consistently between 60°F and 70°F, simulating its native tropical environment. Water actively growing plants more conservatively than in summer, allowing the top two to three inches of soil to dry out between waterings. Indoor heating often creates very dry air, which can be detrimental to actively growing Mandevilla. Increasing the humidity around the plant can be helpful, which you can achieve by misting the foliage or placing the container on a tray filled with pebbles and water.
Dormancy Care
For a dormant Mandevilla, care is simpler. Store the plant in a cool, dark place where temperatures remain around 50°F to 60°F. Dormant plants should only be watered sparingly, just enough to prevent the soil from becoming bone-dry. This may only be required about once a month.
Regardless of the method, refrain from fertilizing the plant during the winter months, as this encourages weak, spindly growth that stresses the plant.
Moving the Mandevilla Back Outside
The transition back to the outdoors in spring is important. Wait until all danger of frost has definitively passed and outdoor temperatures are consistently above 60°F before moving the plant.
The process of “hardening off” is necessary to reacclimate the Mandevilla to harsher outdoor elements like direct sunlight and wind, which can otherwise cause severe leaf burn or shock. Begin by placing the plant in a sheltered, shady location for a few hours daily, bringing it back inside every evening. Over a period of seven to ten days, gradually increase the plant’s exposure until it can remain outdoors full-time.
Once the plant is successfully back in its outdoor location, refresh its growing environment. Repot the Mandevilla with fresh potting mix or top-dress the soil to replenish nutrients. Resume a regular feeding schedule with a balanced, water-soluble fertilizer to encourage new growth and abundant flowers for the season.