Lemon balm is a bushy, lemon scented perennial which is used both fresh and dried to add lemon flavor to salads, soups, sauces, stuffings, poultry and fish dishes. It is also used in some desserts, cordials and liqueurs.
This is a very easy plant to grow but it can become a garden pest (I speak from experience here).
Look for this in the spring and summer at your local farmer's market. Otherwise you may find it at a very well-stocked grocery store. You can also plant from seed, cuttings or buy a small plant at the nursery. It can be grown easily in a pot which will help to keep it contained so it doesn't overtake your garden.
If your recipe calls for fresh lemon balm and you don't have it then there here are some good substitutes:
Alternately you could use one of these options to vary the flavor: