To maintain Mandevilla/Dipladenia, plant in well-draining soil with full sunlight, water regularly but allow the soil to dry slightly between waterings. Fertilize every 4-6 weeks during the growing season with a balanced fertilizer. Prune damaged or dead stems to promote healthy growth and shape. Mulch to retain moisture and protect from temperature extremes. Watch for pests and ensure good air circulation. Deadhead spent blooms to encourage continuous flowering, and bring plants indoors or protect in colder climates during winter.