Compositae Lactuca sativa var. longifolia Lam.
Source: Magness et al. 1971
Cos lettuce develops into an elongated, somewhat oval shaped head. Leaves are elongated, with thick stems and mid-ribs. Heads are only medium firm, and up to 9 or 10 inches in length. Outer leaves, which are largely discarded, enfold the head during late stages of growth. Exposure of the portion usually consumed is similar to that in crisp head lettuce. Cos lettuce is grown much less extensively than the head type. No separate data are available on acreage grown.