Lettuce is an edible, leafy herbaceous biennial that is grown as an annual. The leaves are generally eaten raw in salads and sandwiches, but they can also be grilled. Lettuce is a rich source of vitamin K and vitamin A. Depending on the variety, the lettuce plant can vary in size shape and colour but generally, the leaves form a dense head or a loose rosette, sometimes they are green or red, though there are yellow, gold, greenish-blue and some variegated varieties. The leaves also range from notched, scalloped, frilly to ruffled.