No matter where you are gardening, you can enjoy the gorgeous tropical that is known as mandevilla. In zones 9 to 11 it will winter beautifully outdoors, but the rest of us need to containerize it, and treat it as a houseplant, bringing it indoors during colder seasons when nighttime temperatures reach 50 degrees Fahrenheit.
Plant in well-drained, sandy soil amended with humus. To ensure optimum flowering, place in full sun and water consistently. Because it is such a vigorous vine and flower producer, we recommend small doses of fertilizer every two or three weeks; use a high phosphorus fertilizer (10-20-10) during the spring and summer. Pinch off new shoot tips, which will result in a bushier plant. And as it flowers on new growth, don’t be afraid to trim. Susceptible to mealybugs, scales, whiteflies and red spider mites, keep an eye out for them and treat accordingly.
To prepare for indoor wintering, keep the plant outside until nights begin to cool down in the fall. Then fertilize, strengthening the plant for its winter dormancy, wait about 3 weeks, then prune the vine to one foot above the soil line. Bring inside, watering less frequently; allow the soil to stay a bit dry. After the danger of freezing is over, your mandevilla may be moved back outside, where you and the hummingbirds may once again enjoy this exotic delight.