Lemon grass belongs to a large family of perennial grasses. It grows in clumps of stalks, and resembles green onions in shape. Lemon grass has thin, pointed, inedible leaves. In fact only the bottom, white portion of the plant is used in cooking. The stalk is somewhat woody, and the outer layers are often peeled off and discarded. Lemon grass is most often found in Thai and southeast Asian cuisine and is used to flavor soups and sauces.