Fuschias have a reputation for being difficult to grow, and they are somewhat finicky about growing conditions. They don't tolerate hot, humid weather and need a steady supply of fertiliser and water. However, their exotic blooms usually entice gardeners to keep trying, and with proper care, most gardeners can be successful.
Light and Moisture
Fuschias prefer partial shade, cool temperatures and moist soil. The plants develop yellow leaves and fail to produce flowers in hot, sunny locations. Move the fuschia to a shaded porch with a north or eastern exposure. Water the plant two or three times per week as needed, to keep the soil slightly moist.
Fuschias are heavy feeders, especially when grown in containers that leach nutrients quickly from the soil. Yellow leaves are often signs of too little fertiliser or, more rarely, too much fertiliser. Fertilise fuschias every two weeks with a diluted water-soluble fertiliser.
Aphids, leafhoppers and whiteflies commonly infest fuschias. These insects may suck the juices from the plant, resulting in wilted, yellow leaves. Thrips leave white stippling marks along the leaves. Look for other signs of insect infestation, such as chewed leaves or sticky honeydew on the soil and stems. Spray the plants with insecticidal soap, coating the leaves thoroughly.
Diseases, such as Botrytis blight, rust and crown rot may cause fuschia leaves to yellow, although you'll probably notice other symptoms, as well, such as blackened stems, spots on the leaves or curling leaves. Remove diseased plant material and place the plant in an area where air circulates freely. Do not over water the plant, which can contribute to root rot.