Lettuce (Lactuca sativa), is an annual or biennial herbaceous leafy plant of the Asteraceae family, cultivated for its leaves. Lettuce can vary greatly in size, shape, and leaves, but in general, the leaves of the plant form a dense head. The stem of the plant is short, with large leaves arranged at the bottom that becomes progressively smaller up the stem. The leaves may be smooth or wavy and are usually green or red in color. Lettuce can grow to a height of 30-100 cm and is usually grown as an annual, harvested after a growing season.