There are several types of cos lettuce, and one of the most popular today is Little Gem, which looks like a small, tightly-packed version of the regular cos you'll find on sale.

When buying, ensure the lettuce is a vibrant green colour and that the leaves are standing proud, not droopy and yellowing.

Cos is a good salad base, whether served alone or combined with other leaves. It is essential for true Caesar salad. Thanks to the firm texture of the leaves, it makes a good wrapper for soft savoury mixtures. It can also be cooked (briefly) as a vegetable, and made into soup.

Aim to eat lettuce as soon as possible after picking or purchase. If you absolutely must store lettuce, leave it whole. Remove any plastic bags to stop it sweating and keep it cool and dark in the salad drawer of the fridge.