Some tips for growing Mandevilla spendens include planting it in well-drained soil, choosing a site with full or partial sun, and amending the soil with organic material. Keep the soil between a 6.6 and 7.8 pH, or add limestone to increase the alkalinity.
Before planting mandevillas, select a site that preferably has partial shade and sandy soil. Work a generous amount of organic material into the soil to increase drainage, and add limestone or sulfur to bring the pH to the required levels. Because mandevillas reach up to 6 feet in height, plant them at least 36 inches apart to allow the shrubs plenty of room to grow. If your location has cool winters that fall below 45 degrees Fahrenheit, plant the mandevillas in a pot that can be brought indoors during cold weather. Place a trellis beside the mandevillas to serve as a support structure.
During the growing season, make sure that the temperature stays between 60 to 70 degrees Fahrenheit during the night and day respectively. Water the mandevilla plants regularly so that the soil remains evenly moist. Fertilize the plants twice a month with a phosphorus-rich fertilizer. Control growth and increase air circulation by pruning the plant in the early spring, avoiding trimming new growth.