Containerized indoor citrus trees often begin producing fruit between 1 and 3 years of age. Varieties that perform well as indoor specimens include dwarf tangerine, key lime, Meyer lemon, dwarf navel orange, pink Eureka lemon, Oro Blanco grapefruit and Kaffir lime. You'll probably find that even the nastiest of winter days won't seem quite so dreary while sharing your home with your cheerful, fragrant, containerized citrus tree.
Choose the container for your indoor citrus tree, typically one to two sizes larger than the plant's current pot. A 3-gallon container is usually sufficient for a seedling, while the plant will probably need a10- to 15-gallon pot when fully grown. When roots begin poking out of drainage holes, it's time to step the plant up a pot size.
Layer the bottom of the container with broken pottery or stones to encourage good drainage. Use a light, all-purpose potting mix containing perlite, but never use garden soil. Plant the tree at the same depth that it occupied in its former container. Add water until it begins to seep from the drainage holes.
Set your citrus tree in the sunniest room of your home. These plants require eight to 12 hours of sunlight daily to thrive. Without enough light, the leaves will probably drop, and the plant will become leggy, unhealthy and unattractive. Strong fluorescent lighting can be substituted if absolutely necessary.
Continue to water the indoor containerized citrus tree when the top couple of inches of soil become dry, but don't ever allow the roots to completely dry out. Stick your finger 2 to 3 inches into the soil. If it's dry, the plant needs water. A single incident of excessive dryness can kill your tree. Yellowing leaves is an indicator that the plant is either being overwatered or that draining is inadequate.
Mist the foliage generously every day, if at all possible, to provide necessary humidity. This is particularly important if you live in a dry climate or when indoor winter heating dries the air excessively. Adding a humidifier to your home is very helpful, or spread some gravel in a shallow pan and just barely cover it with water. Set the plant on top of the gravel, which will provide more humidity. Increasing the amount of available moisture in the air not only contributes to the plant's health, it also helps reduce some pests in indoor tropicals.
Feed your citrus tree a good slow-release 2-1-1 fertilizer every other week throughout the growing season, beginning in early spring. These plants require lots of nitrogen, as well as iron, zinc and manganese.
Pollinate your blooming indoor citrus so that it will produce fruit. Dab stamens--the filaments that hold the grains of pollen--of a fully opened blossom with a soft craft paintbrush or cotton swab to gather some of the pollen. Brush the inside centers of the other flowers with it, so that each is likely to develop into a fruit.
Prune out deadwood and any branches that criss-cross each other, which will encourage good air circulation within the plant's interior. Remove any suckers--branches that sprout below the point of desired branching--that may appear. You can prune your indoor containerized citrus tree at any time during the year without injury to the plant.
Move your containerized citrus outdoors to enjoy warm, sunny spring and summer weather. You'll need to acclimate it to the change gradually, beginning by placing it in a sunny or lightly filtered spot early in the morning each day for a week after there's no longer a threat of frost. Bring your plant back inside about noontime, and return it to its indoor spot for the remainder of the day.
Set your citrus tree out from early morning until dusk during the next week. If sustained overnight temperatures remain above 60 degrees Fahrenheit, it can stay out the rest of the night. Otherwise, bring it in after dusk until the nights warm up sufficiently. It's possible for the plant to go dormant if exposed to extended temperatures below about 55 degrees Fahrenheit.