Lemon grass, Cymbopogon citratus, is a tender perennial that is treated as an annual in Minnesota. At the end of summer, it should be cut back and brought indoors to overwinter. Lemon grass is purchased as a plant. It is an essential ingredient in Thai and Southeast Asian cuisine. It has a subtle citrus, nutty flavor that is used in soups, stews, and stirfry. Use as a flavoring only, because the plant is tough and, like a bay leaf, not meant to be eaten.