They enjoy bright, indirect light or filtered sunlight, but can get burned in direct, full sunlight. In order to get the best Mandevilla flowers throughout the summer, give your Mandevilla plant a high phosphorus, water-soluble fertilizer once every two weeks. This will keep your Mandevilla vine blooming wonderfully.
Light conditions: Provide direct sunlight for at least several hours daily.
Watering: Mandevilla prefers regular amounts of water, whether indoors or out. Water your plant weekly with a deep soaking until you see moist soil, or water draining from container plants. Keep the soil moist, but not dripping wet, and make sure it's well-draining; cut back on watering during the winter when growth slows down, letting the soil dry out more between waterings. If it takes longer than 30 seconds for the water to soak into the soil, consider repotting or replanting the plant. Add sand or perlite to the soil to help with draining, and make sure plant containers have good drainage holes.
Feed your Mandevilla vine every two weeks during the growing season with an all-purpose fertilizer or with one higher in phosphorus than other nutrients, such as one labelled 10-20-10
Rate of growth: Fast
Proper Pruning: You can pinch the tips of Mandevilla with your fingers at any time to encourage bushy growth and keep the vine from trailing too far. Prune more in the spring before new growth begins, cutting off older or crowded stems and shortening others to control the size of the plant. New growth will come in the spring, even if you cut the stems back all the way to the ground.
Humidity: High humidity, can possibly tolerate average humidity but mileage may vary.
Temperature: minimum 10C (50F)
Pests and Disease: Mandevilla vines are not plagued by serious diseases, but they can become infested with whiteflies, spider mites or mealybugs. Examine your vine every few weeks to look for bugs or larvae, and cut off any diseased leaves or stems. If you see bugs, hose them off with a strong spray of water, or use an insecticidal soap or oil as directed on package labels.