King Louis XIV of 17th century France had the right idea---he built a large glass greenhouse called an "orangerie" at his Versailles palace. In winter, his 3,000 orange trees lived indoors and when the weather warmed up in spring, his minions dragged the potted fruit trees into an open-air courtyard to gain the benefits of the sun. The advantage to growing an orange tree in a container is that you can follow Louis' lead by protecting your tree from winter cold and then moving it outdoors during warmer weather.
Growing Orange Trees in Containers
Pot a dwarf orange tree in your large container. To improve drainage, which all citrus trees need, first spread a one-inch layer of pebbles or gravel in the bottom of your pot. Then fill it about halfway with a lightweight potting soil mix.
Empty your orange tree from its nursery pot and gently loosen the roots, especially if the tree has become rootbound. Set it on top of the soil in the container, making sure that the top of the soil will cover the roots without covering the beginning of the trunk, where a graft is often found.
Fill your pot with more potting soil, completely covering the roots but not burying the base of the trunk. Pat the soil down gently to help it to settle, and then water your new tree well.
Water your potted orange tree when the soil becomes slightly dry---once each week or two is usually adequate. It's wise to check the soil at the bottom of your pot with a moisture meter because orange trees can die of root rot if their roots are kept too wet.
Fertilizer your potted orange with a plant food specifically formulated for citrus. Because oranges need plenty of nitrogen, the N-P-K ratio of an appropriate fertilizer should be at least 2-1-1. Commercial fertilizers for acid-loving plants are available and often have an N-P-K ratio of 3-1-1.
Cut off any suckers that form at the base of your orange tree, but be careful not to cut them off above the graft, which is usually 4-8 inches above the soil line. Doing this will give the tree more vitality by not allowing it to put its energy into growing suckers.
Keep ants under control by smearing a product called Tanglefoot around the lower trunk of your tree according to label instructions. Ants bring destructive insects such as aphids and scale to the foliage. If you notice aphids or scale, first spray your tree with a sharp stream of water to remove as many insects as possible and then spray it with insecticidal soap twice a week until all signs of insects are gone.
Hang fluorescent shop lights or a grow light above your orange tree after you move it indoors for the winter to give it the light it needs to remain healthy until spring. The more natural sunlight it gets during winter, the better, so if you keep it near a sunny window, it will thrive. Also, reduce watering while your orange tree is in its winter home.