Miniature oranges (Citrus sinensis) are only hardy in U.S. Department of Agriculture plant hardiness zones 9 and warmer, so unless you live in citrus country, your citrus trees must be grown indoors. Fortunately, citrus trees thrive indoors under the right conditions and provide the added benefit of filling a room with the beautiful scent of flowers when they bloom. The whole family will enjoy watching the tiny buds transform into mature fruit, and children are more likely to eat fruits and vegetables when they are involved in the growing process. Keeping dwarf citrus in the correct size pot ensures healthy root development and overall growth.
Moving to a Larger Container
Miniature citrus grows at a moderate rate, but if you see growth on the top of the plant, then the roots are growing as well. Move your tree to a larger pot every two or three years to prevent it from becoming root bound. If the roots do become bound, growth may be stunted. Don't worry if this happens, just transfer the plant to a new pot and feed it with citrus fertilizer according to the package instructions. Keep the soil moist, but not wet, and the roots should begin to grow again. For a while, the plant's energy is focused on growing new roots, so it may take some time before you see new top growth.
Prevent Stressed Plants
Plants grown entirely indoors can be transplanted any time of the year because they do not encounter environmental stress. If you plan to move your tree outdoors for the summer or in for the winter, avoid transplanting during the adjustment period. The change in environment causes some stress to the plant, and transplanting creates more. Wait a few weeks after transitioning indoors or out before transplanting. Never transplant during or after pest issues or any fungal diseases. Only transplant healthy, unstressed trees.
Providing the Right Soil Environment
Terra cotta, plastic or wooden containers are all fine for growing miniature citrus. The most important thing to look for when selecting a container is excellent drainage. It is better to have too many drainage holes than not enough; they just need to be small enough to hold soil but large enough for water to move through if necessary. If you are considering moving your citrus outdoors in the summer, use a lightweight planting medium such as a mixture of half peat moss and half high-quality potting soil. Commercial potting mixes specifically formulated for citrus or cactus also work well. Wear gloves whenever you work with soil, planting mediums or amendments to guard against soil-borne pathogens.
Best Growing Conditions
Place plants in front of a sunny, south-facing window or use a grow light, turning it on at sun up and off at sunset. During the dry winter months, place a humidifier near the tree to keep the leaves from drying out. Use a fertilizer specially formulated for citrus trees according to package instructions. Soil should be moist, but not wet, so only water when the soil is dry 6 inches below the soil line.