Lettuce (Lactuca sativa) is the fourth most important vegetable crop grown hydroponically in greenhouses preceeded by tomatoes, European cucumbers, and peppers. Although greenhouse production of lettuce is very small in comparison to field grown, it has a specific market niche as a gourmet, high-quality item. Boston Bibb lettuce, the type we grow, has a soft head, not the dense compact head of “iceberg” or head lettuces. Being clean and free of soil, it is particularly popular in restaurants.