in taxon romaine lettuce head 2019-06-27T13:30:10Z https://en.wikipedia.org/wiki/Romaine_lettuce https://upload.wikimedia.org/wikipedia/commons/thumb/5/5c/Starr_070730-7911_Lactuca_sativa.jpg/320px-Starr_070730-7911_Lactuca_sativa.jpg Damion Dooley A rosette of a romaine lettuce plant (Lactuca sativa var. longifolia). Lactuca sativa L. var. longifolia Romaine or cos lettuce is a variety of lettuce that grows in a tall head of sturdy dark green leaves with firm ribs down their centers. Unlike most lettuces, it is tolerant of heat. cos lettuce romaine lettuce head (anatomical) Lactuca sativa var. longifolia rosette ready for release