Orange trees grow and fruit in pots, blooming with fragrant white flowers in spring and providing evergreen, glossy foliage all year. As potted plants, oranges are decorative indoors and on patios or decks. Cultural requirements for this subtropical citrus plant, which grows in Mediterranean climates and U.S. Department of Agriculture plant hardiness zones 9 through 10, include full sun or bright light, a high accumulation of heat hours for fruiting -- accomplished by putting the tree outside in the sunshine from spring through fall whenever temperatures stay above 26 degrees Fahrenheit -- and providing water and fertilizer routinely. With attention to potting details, orange trees in pots last for years.
Orange Tree Selection
Small trees suited to container planting include orange tree varieties grafted onto dwarf rootstock, which is generally either trifoliate orange (Poncirus trifoliata) or its cultivar "Flying Dragon." Trifoliate orange root stock produces trees with a growth potential of approximately 10 feet tall, while "Flying Dragon" produces 5- to 7-foot tall trees. Satsuma is a seedless variety of mandarin orange (Citrus reticulata) that grows to only 6 feet tall. When protected against temperatures below 26 degrees Fahrenheit and given eight to ten hours of sunlight each day, satsumas can be successful when potted. "Trovita" sweet orange (Citrus sinensis) on dwarf rootstock reliably produces fruit when container-grown and given basic cultural needs of six to ten hours of sunlight, regular watering and fertilizing.
Pots and Potting Mixtures
Orange tree pots must have good drainage provided by holes in the bottom of the pot, and the pot should be elevated to allow free drainage. A pot should fit the root size, making it easier to manage moisture levels. One-year-old trees grow well in 6- to 9-inch-diameter pots with an equal depth. Trees that are two to three years old generally perform best in 12-inch-diameter containers. Older trees can be grown in half whiskey barrels, or 20-gallon pots. Once your tree reaches the maximum desired size, root pruning can maintain the tree's size indefinitely. To root prune, an orange tree is lifted out of its pot and the outer 2 to 3 inches of roots are removed, and loose soil is shaken out of the root ball. The container should be cleaned thoroughly and the tree replanted in fresh potting mixture. One successful citrus-potting mixture is a commercial soil-less mix amended with one part of cedar or redwood chips, perlite or coco fiber to three parts potting mixture.
A moist, well-drained potting mixture that dries out in the upper 1 to 2 inches of the mixture before the tree is watered keeps an orange tree properly hydrated without waterlogging or drying out the roots. Potted orange trees require less water in cool weather, as moisture does not evaporate as quickly when temperatures are low. Irrigation should be thorough, allowing water to drain out the bottom of the pot with each watering.
Nutrient requirements of potted orange trees include high-nitrogen fertilizer and trace minerals, such as zinc, iron, manganese, boron, molybdenum and copper. Label instructions for slow-release fertilizers generally recommend application every two months while water-soluble fertilizers are applied every two weeks. The rootstock of grafted trees determines the pH level preferred by specific orange trees. Ask the grower or seller for recommendations on pH requirements.
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