How to grow Lemon Balm Seeds
Sow lemon balm seeds from late March to May on the surface of a good seed compost and cover with a sprinkling of compost or vermiculite. Place the seed tray in a propagator at a temperature of 20-25C or seal it inside a polythene bag. Keep the compost slightly dry at all times. Do not exclude light as this aids germination which usually takes up to 21 days.
When seedlings are large enough to handle, transplant and grow them on in cooler conditions until large enough to plant outdoors. When lemon balm plants are well grown and all risk of frost has passed, acclimatize them to outdoor conditions over 7 to 10 days. Transplant outdoors in full sun on any moist, well drained soil at a distance of 30cm apart. Lemon balm plants will tolerate poor soils. This herb is vigorous, but growing lemon balm in containers will help to restrict its growth.
Watering:
Keep plants well-watered during the growing season, especially during dry spells. Plants need about 2.5cm of rain per week during the growing season. Use a rain gauge to check to see if you need to add water. It’s best to water with a drip or trickle system that delivers water at low pressure at the soil level. If you water with overhead sprinklers, water early in the day so the foliage has time to dry off before evening, to minimize disease problems. Keep the soil moist but not saturated.