Mandevilla Is Turning Brown

Cold Exposure

• Mandevilla prefers warm temperatures and cannot withstand freezing weather. It may suffer from damage if the temperature falls below 45 to 50 degrees Fahrenheit, according to Clemson Cooperative Extension. In colder zones, keep Mandevilla plants in containers and bring them indoors during cold weather. They can be returned outside after the threat of freezing weather is over.

Underwatering

• Too little water can cause Mandevilla buds to turn brown and die. This plant needs evenly moist soil during the growing season. Water Mandevilla plants regularly to keep the soil damp, but not saturated or sopping. If one of these vines seems to dry out easily, shade it from the hottest afternoon sun and water more frequently until the plant recovers.

Root Damage

• Mandevilla plants suffering from root damage can't draw up the nutrients they need to survive. Too much water or a poorly-drained soil may damage the roots. Wet conditions also encourage bacterial and fungal infections that rot the roots. Water only enough to keep the soil continuously moist and keep the vine in soil containing equal parts potting mix, peat moss and builder's sand. Avoid planting Mandevilla in dense, clay soils, as these keep the roots wet.

Poor Nutrition

• Nutritional deficiencies cause plant leaves to turn yellow, brown and fall off completely. In severe cases, the plant may die. According to the National Gardening Association, Mandevilla plants require regular fertilizer applications during the growing months. Use a 10-10-10 or 10-20-10 water soluble fertilizer, or a slow-release product. Apply the fertilizer every two weeks.

Transplant Shock

• Moving plants damages their roots and shocks their systems. A Mandevilla plant moved during the growing season, rather than while it is dormant for winter, will suffer from significant growth problems and may lose its leaves. When possible, move Mandevilla vines carefully and in the dormant season. Treat a plant suffering from transplant shock by keeping the soil moist. Add a layer of mulch or compost to encourage the roots to resprout, and provide fertilizer on a regular schedule.