Lemon trees actually make good houseplants while the trees are still in seedling form; they can grow under indoor growing conditions if there is enough sun in the house. You can grow a lemon tree from seeds harvested from any lemon purchased at a supermarket or picked right off an adult lemon tree. It takes several years for a lemon tree to grow large enough to sprout blossoms and a few years after that before it will grow lemons.
Purchase a lemon with seeds. Not all lemons sold at the store come with seeds. Purchase two or three of a seeded variety to ensure that you get enough seeds to save in case some do not sprout.
Remove the seeds from the lemons. Don't use a knife to remove the seeds as the knife can damage the seed casings. Try to remove the seeds by hand by squeezing the pockets of the lemon and extracting the seeds.
Rinse the seeds in water and place them on a paper towel. Pick out the seeds that are the largest. The seeds that are more white than tan with a shriveled coating on them are the best choices for growing a plant.
Moisten a paper towel and place the seeds on the towel. Keep about three times the amount of seeds you actually want to plant in case some are duds. Wrap the seeds in the damp paper towel.
Place the towel and seeds inside a plastic sealable sandwich bag. Place the bag in the refrigerator. You can keep the seeds inside the refrigerator for several days or several months until planting time.
Remove the seeds from the refrigerator and plant 1/2-inch deep in soil when you want to sprout the seeds. You can also sprout the seeds on a moist paper towel bed. The seeds will sprout best if grown indoors in a warm, sunny location in nutrient-rich soil.