24 to 30 days. Lemon Balm microgreens seeds, when grown as microgreens, are quite beautiful with a serrated edge and a pale maroon reverse. Patience is required when growing this herb microgreen. Lemonbalm microgreens are a long-term grower, taking up to a month to reach microgreens harvest stage. From a wonderful fragrance to a subtle lemon flavor with a hint of bitterness, this long-term micro is well worth growing. Try it in a favorite marinade or vinaigrette.