The Mandevilla, often sold as Dipladenia, is a tropical vine valued for its striking, trumpet-shaped flowers in shades of red, pink, and white. This South American native offers vibrant, glossy foliage and continuous blooms, making it a sought-after container plant. For those in temperate climates, growing Mandevilla indoors preserves this tropical beauty year-round. While the plant can be demanding, providing specific conditions allows it to flourish inside a home environment.
Creating the Ideal Indoor Environment
Mandevilla requires sustained periods of bright light to flower indoors, ideally a minimum of six hours of direct sunlight daily during the growing season. Positioning the container near a south or west-facing window is generally necessary to meet this demand. However, intense midday sun in the summer can cause leaf scorch, so a sheer curtain or slight offset from the window may be required for protection.
Mandevilla thrives in warm conditions, reflecting its tropical origin, and should be kept away from cold drafts or direct heat sources like vents. During the day, temperatures ranging from 65 to 85 degrees Fahrenheit (18 to 29 degrees Celsius) are optimal for active growth and blooming. Nighttime temperatures should not drop below 50 degrees Fahrenheit (10 degrees Celsius), as this can shock the plant and lead to severe foliage damage.
The plant prefers humidity levels in the range of 50 to 60 percent, which is often higher than typical indoor air, especially during winter. To compensate, place the pot on a tray filled with pebbles and water, ensuring the pot bottom sits above the water level. Regular misting or using a small room humidifier positioned nearby will help replicate the moist tropical environment.
Essential Soil and Hydration Practices
The growing medium must be both moisture-retentive and fast-draining to prevent root issues. Standard potting mix is often too dense and should be amended with materials like perlite, coarse sand, or bark fines to increase aeration. This structure allows oxygen to reach the roots while ensuring excess water flows freely. Use a pot with ample drainage holes to avoid “wet feet.”
The plant prefers consistently moist soil during its active growing phase but quickly succumbs to root rot if overwatered. Check the soil regularly, watering thoroughly only once the top one to two inches of the potting mix feel dry to the touch. While summer heat may require watering every few days, frequency decreases significantly as light levels drop in cooler months.
Regular feeding is required throughout the spring and summer to support continuous flower production. Use a water-soluble fertilizer with a high phosphorus content, which encourages bud formation over vegetative growth. An NPK ratio that favors the middle number, such as a 10-20-10 formulation, should be applied every two to three weeks. Stop fertilization entirely in the fall and winter to signal the plant to slow its growth cycle.
Structural Maintenance and Training
Mandevilla requires a physical structure to climb, even when grown indoors. Installing a small trellis or providing stakes within the pot allows the twining stems to ascend and prevents sprawling. Gently wrap the flexible, new growth around the support structure by hand to encourage a neat, vertical habit that saves space.
Pruning maintains the plant’s shape and promotes a denser, bushier appearance. Throughout the active season, “pinch” the ends of new stems by removing the top quarter to half-inch of growth. This removes apical dominance and forces the plant to divert energy into lateral buds, resulting in a more compact, branching form. Substantial pruning is reserved for the pre-dormancy period in the fall to prepare the plant for indoor rest.
Addressing Common Indoor Challenges
Mandevilla is susceptible to common houseplant insects, including spider mites, mealybugs, and scale, which thrive in the low-humidity conditions of heated homes. Thoroughly inspect the undersides of leaves and stem joints, especially before bringing the plant indoors for the winter. Treatments such as insecticidal soap or horticultural oil, like neem oil, should be applied weekly until the infestation is controlled.
The process of overwintering is the most complex aspect of year-round care in cooler climates. When outside temperatures consistently fall into the 50s Fahrenheit, the plant must be moved inside. Gardeners have two main options: maintaining it as an active houseplant or forcing a semi-dormant state.
Active Houseplant Overwintering
To overwinter as an active houseplant, the Mandevilla needs the brightest possible light, supplemental humidity, and a warm temperature of 65 to 70 degrees Fahrenheit. Reduce watering, providing moisture only when the top inch of soil is dry. Any fertilizer applied should be at a diluted strength.
Semi-Dormant Overwintering
Alternatively, the plant can be forced into dormancy by pruning the vines back by one-third to one-half. Store it in a cool, dark location where temperatures remain between 50 and 65 degrees Fahrenheit. In this dormant state, water very sparingly—only enough to keep the potting mix from drying out completely. Leaf drop is a natural reaction to the reduced light and temperature.