Typically, lemon trees flourish outdoors year-round in hot, sunny regions, but they can also thrive indoors as edible houseplants in cold-season climates. At the organic food store where I work we have a healthy lemon cutting producing massive fruit in a garage setting all year.
And although it may take anywhere from 3-6 years for your tree to be capable of producing fruit, there is something extra rewarding about starting from seed.
A lemon. Make sure you purchase an organic lemon since some non-organic lemon seeds may be “duds”, incapable of germinating. Any organic lemon will do, but if you have climate or space restrictions, you may want to try looking for a specific variety called a “Meyer” lemon. Meyer lemons are a smaller type of lemon, often grown for ornamental purposes, and are thus better suited for indoor containers.
Container/pot. A container (with drainage holes) that is 5-6” deep and a few inches in diameter will be sufficient for sprouting; however, the seedling will need to be re-potted into a much larger container.
A grow light or lots of sun. Lemon trees need a lot of light, especially when they are sprouting and require 10-14 hours of it each day. If you don’t have a consistently sunny window, get a grow light. They don’t cost much and will prove their worth in healthy green foliage.