It may seem incredible that citrus trees can grow and thrive in an indoor climate, but it can be done, and fairly easily. There's no reason you can't grow an orange, lemon or lime tree, even in limited space, as long as you are able to provide plenty of sunlight and humidity. The leafy green foliage will brighten up any room, and when the tree blooms, the sweet scent will fill the air. Although indoor citrus trees are mostly ornamental, if you're lucky, your indoor citrus may even provide some delicious fruit.
Visit a greenhouse or garden center and purchase a healthy citrus tree. Look for dwarf or ultra-dwarf varieties that are suitable for indoor growing. Regular-sized citrus trees are difficult to grow indoors, and will need constant pruning and frequent re-potting. Select trees with straight trunks and sturdy branches that grow outward. Avoid trees with any discolorations or oddly-shaped branches.
Choose a container slightly larger than the tree's root system. Fill the container with good quality potting soil, and mix in a scoop of rotted manure or compost.
Create a mound in the middle of the planting container. Remove the citrus tree from its nursery container or wrapping, and spread out the roots. Place the roots evenly over the mound, and fill the container with potting soil, up to the soil line on the trunk of the tree. Water the tree immediately after planting.
Put the citrus tree in bright sunlight. Citrus trees need a minimum of five hours of bright sunlight every day, although 8 to 10 hours of sunlight is optimum.
Keep the citrus tree in a warm room. Citrus trees will do best in daytime temperatures between 75 and 90 degrees, and between 60 and 70 during the fall and winter months. Never let the temperature drop below 45 degrees. If the air in the room is dry, turn on a humidifier for a few hours each day.
Water the citrus tree just enough to keep the soil moist. Don't overwater the tree, and allow it to dry out slightly between each watering.
Fertilize citrus trees monthly between April and September, using a fertilizer formulated especially for citrus trees. Don't fertilize during fall and winter, when the tree is dormant.
Prune trees as needed. Dwarf citrus trees need very little pruning, so prune them to maintain their shape. Clip off any branches that are growing too long, and remove any branches that are growing inwards, or across other branches.