Lemon balm seeds are easy to start in early spring. Plant them in well-draining, rich soil in a spot that gets part shade to full sun. Keep the soil moist but not waterlogged. In the United States, you can sow seeds directly outdoors after the danger of frost has passed, or start them indoors 6-8 weeks before the last frost date. Lemon balm is a member of the mint family and grows vigorously, so consider planting it in small pots or contained areas in your herb garden.