Lemon balm is an herb in the mint family that grows well indoors in containers. One of the few herbs that prefers low-light conditions, lemon balm may be used to make a medicinal tea that some have touted as a treatment for fever, headaches and to aid digestion. Lemon balm essential oil may be used as an aromatherapy treatment for depression and anxiety. Mature lemon balm plants grow up to 2 feet tall with oval or heart-shaped leaves that grow up to 3 inches long.
Fill seed trays with perlite, vermiculite, rockwool or other soilless potting medium. Moisten the growing medium. Place two to three lemon balm seeds on top of the growing medium in each tray. Cover the seeds with a light layer of the same growing medium.
Place the seed tray beneath fluorescent lights or grow lights. Keep the seeds moist, but not wet, as they germinate. It takes approximately six weeks for the seeds to germinate into finished plugs (small plants).
Fill a planter with potting soil, up to within 2 inches of the top rim. Remove the lemon balm plugs from the seed tray. Place two to three plugs into a 9- to 14-inch diameter planter. Space the plugs about 3 inches apart. Water the newly planted lemon balm well.
Place the planted container of lemon balm beneath fluorescent grow lights or in a sunny windowsill. Lemon balm grows well in partial shade outdoors and low light indoors. Standard fluorescent lights should hang as between 2 and 4 inches above the plants; compact and high-output fluorescents can hang 1 foot above the plants. Lemon balm needs at least 6 hours of light each day.
Set an oscillating fan to provide air circulation to the plants for up to two hours each day. Increased air circulation will help the lemon balm grow sturdier and shorter.
Water the lemon balm on a consistent schedule to keep the soil moist. Fertilize lemon balm with nitrogen-rich fertilizer every six to eight weeks.
Pinch the flowers from the lemon balm plants as they appear. Lemon balm will self-seed if you do not remove the flowers.
Harvest the lemon balm leaves from mature plants once or twice each week. Frequent trimming will help the plant lemon balm grow into a compact plant.