About: Lettuce has been cultivated for thousands of years as supplemental food stuff and has become a staple in most cultures as the perfect leafy green to serve alongside favorite main dishes. Lettuce is a source of Vitamins K and A, although some are better than others. Cos lettuce is a variety of lettuce that grows in a tall head of sturdy dark green leaves with firm ribs down their centre. Unlike most lettuces, it is tolerant of heat. Eat: Mainly eaten as the base to salads, it can be roasted, made into soup and added to smoothies, it is great for filling as a wrap.