A citrus tree is an ideal plant for a warm, sunny room. Their dark, shiny leaves and fragrant blossoms add to the appeal of their brightly-colored, ornamental fruit. From a size standpoint, the smaller members of the citrus family such as limes, Meyer improved lemons, kumquats and calamondins are the best choices for house plants, but all citruses can adapt to containers.
A container must be large enough for the citrus to grow and have drainage holes in the bottom. It is recommended that the plant be repotted annually into a slightly larger pot. If a plant fails to bloom adequately, skip repotting for a year. Slightly crowding the plant may help to force blooms.
Citrus grows best in full sun. In the home, potted citrus should be placed in a southern or western window where it will receive an adequate amount of sunlight every day. Anything less than full sun won’t kill the plant but may result in less yields and lower quality fruit.
When the soil is almost dry (allow to dry between waterings), water the tree thoroughly so that the entire root ball is drenched. Citrus requires high humidity, especially when blooming. This can be achieved by misting daily, standing the plant on a pebble tray full of water or using a humidifier.
Premixed, sterilized potting soil is the ideal for citrus planted in containers. It is vital for the soil to be well-drained. Avoid using soil from your garden because while it may work well outside, it will be too densely packed in a container to allow proper drainage. Adding sand to the soil will also help with drainage.
Citrus prefer slightly cooler temperatures than the average home; 50 to 55 F at night and 68 F during the day.
Fertilization is recommended at least three times per year: early Spring, early Summer and late Summer. Use an acid-based fertilizer such as Miracid or a well-balanced N/P/K fertilizer applied no stronger than the recommended rate.
Prune tip growth at any time to keep the citrus compact and bushy. The ideal time to prune citrus is in the early spring. Although most citrus do not require major pruning, it is still advised to trim any excessive growth.
While many citrus varieties are self-pollinating, growing them indoors may require you to pollinate them yourself in order to yield the desired fruit productions. This process is a matter of taking the pollen grains from the anthers (male parts that stick up around the center) of flowers and, using a cotton swab, small paintbrush or fingertip, dabbing it directly onto the sticky center of the flower called the stigma (female part). Repeat the process for any flowers that you would like to see produce fruit.
While citrus grown outdoors will be exposed to natural elements (like other insects) that will devour pests, indoor citrus, if infested, can become overwhelmed. Pests may include aphids, mites, scale and mealybugs and are typically a sign of poor plant care (overwatering, poor soil drainage, lack of soil nutrients). If container size and season allows, one way to alleviate this is to put the plant outside. An alternative is to wash the plant outdoors or in an indoor sink or shower with an insecticidal soap solution such as Bon-Neem by Bonide. If the plant has been brought outside, soap treatment is recommended before bringing it back inside to eliminate the possibility of new insects taking up residence. If infestation is severe, composting the plant and starting anew may be the best plan of action.