hardy biennial plant (Allium porrum) of lily family (Liliaceae); related to onion; mild, sweet flavor; leaves arise from compressed stem and overlap concentrically in nearly cylindrical bulb in first season of growth; tuft of roots grows from base; in second season, tall, solid stalk arises bearing leaves and large globular umbel with many perfect flowers; seeds are small, black, and irregular; widely used in European soups and stews; native to e. Mediterranean lands and Middle East; national emblem of Wales, worn in hat on St. David's Day (March 1).