Among the group of lettuce
*The Cos or romaine forms an upright, elongated head and is an excellent addition to salads and sandwiches.
*The Cutting group or leaf group forms no firm heads but instead produces a dense mass of leaves in the center of the plant.
*The Stalk lettuce group does not form heads and has prominent thickened fleshy stems and upright ovate leaves.
*The Butterhead group are generally small, semiheading types that have tender, soft leaves and a delicate flavor.
*The Crisphead group forms tight, dense heads which are comprised of spherical leaves folded upon each other. The leaf is crispy and the veins are prominent. Crisphead lettuce also is commonly referred to as iceberg lettuce. Crisphead has a large solid head similar to a cabbage.
*The Oilseed group is typified by a multistemmed upright growth habit with green leaves that are oblong to oblanceolate.
The three main lettuce types produced in the United States are iceberg (L. sativa L. var. capitata L.), romaine (L. sativa L. var. longifolia L.), and leaf (L. sativa var. crispa L.).
Mature plants of marketable quality are individually harvested. Iceberg lettuce for whole head production has traditionally been harvested at market maturity. Romaine reaches market maturity as fast or faster than iceberg, and leaf reaches market maturity faster than romaine.
Lettuce
