Lemon trees are commonly grown in warm, sub-tropical regions that are similar to their natural habitat. However, they can fully mature and bear edible fruit indoors if the environmental conditions are properly emulated. Lemon trees will grow to a height considerably smaller than those grown outdoors due to the size of the planter, usually no larger than 3 to 5 feet. Lemon trees are easy to care for in every climate when brought indoors and require only minimal maintenance to thrive.
Fill a planter with a medium made of two parts potting soil and one part peat moss. This will increase the fertility and drainage of the soil. Sow the lemon tree seed in the soil about 2 to 3 inches deep and water lightly to collapse any air pockets in the soil.
Place the planter in a window that receives about four hours of bright sunlight per day. Ensure the temperature stays between 50 and 80 degrees Fahrenheit at all times. Water once every two weeks until the seed germinates and growth emerges from the soil.
Set a humidifier near the lemon tree to raise the relative humidity. Lemon trees need a fair amount of moisture in the air to grow properly. Keep the humidifier running at all times to ensure the humidity stays constant.
Water indoor lemon trees once per week, allowing the soil to dry slightly between applications. Reduce watering to once every two weeks during winter when the temperatures are lower. Avoid over-watering but never allow the soil to completely dry out.
Feed lemon trees using a balanced 10-10-10 NPK fertilizer once every two weeks. Water thoroughly both before and after application to prevent nitrogen burn. Follow the manufacturer's directions for proper dosage.
Pollinate lemon trees during the blooming season to induce the growth of fruit. Use a cotton swab to gently collect pollen from an open flower. Deposit the pollen in a separate flower and fruit will begin to form after several weeks.