Mandevillas are tropical plants that love heat and regular water. They can be overwintered indoors in a sun room if you do not live in a tropical climate.  Poke your finger into the soil and water when the top one inch of soil is dry. The timing depends on your weather and soil. The like a slow release plant food like Osmocote added to the soil in late spring or early summer. In a cool summer area this plant will bloom best when grown against a west or south facing wall that absorbs heat. Keep growing, Marianne Binetti