For optimal growth, fertilize banana plants in containers monthly with a balanced fertilizer that provides nitrogen, phosphorus and potassium in equal proportion. Fertilizers such as 5-5-5 or 10-10-10 are good choices for banana trees. For banana plants growing outdoors in the ground, fertilize them less frequently, every two to three months, with 6-2-12 fertilizer. Fertilize them once a year with zinc and manganese.
Banana plants have small root systems, so apply the fertilizer close to the base of the plant. If using water-soluble fertilizer, dilute it to half strength. If a mature plant has fewer than 10 to 12 leaves or does not produce fruit, this can be a sign of insufficient nitrogen. If the leaves are misshapen, this can indicate over-fertilization.
Though banana plants cannot survive the winter in most parts of the United States, their small roots systems make them ideal for containers. Grow them in containers on the patio, and bring them indoors when nighttime temperatures drop below 67 degrees Fahrenheit, or grow them indoors all year in a sunny area of the home, such as near a south-facing window. A 6- or 8-inch pot provides sufficient space for young plants.
In addition to fertilizing, water the plants when the top of the soil begins to dry in containers or weekly for outdoor plants.