Lemon Tree Growing Indoors. Lemons can make excellent houseplants and will be comfortable in a container as long it provides adequate drainage and room for growth. Heights of around 3 to 5 feet can be expected for a lemon tree growing indoors. They also prefer well-draining, slightly acidic soil. Keep the soil evenly moist and fertilize as needed. Lemon trees thrive within a normal temperature range of about 70 F. (21 C.) throughout the day and 55 F. (13 C.) at night.